Starglider
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An XB-70 AV-2 Question.

Wed Dec 06, 2006 7:59 am

Does anyone know what the purpose was of the fairing that was installed at the RH wing root of the second XB-70 prototype AV-2, # 20207?
This fairing was installed at the right side only and started above the RH landing gear wheel bay and ran all the way back to the "boat tail" where it appeared to fair back into the fuselage/engine compartment. No such fairing was installed on the LH side, nor did i ever see it installed on the first prototype.


See image with detail below.

Any suggestion is appreciated,
Starglider.


[Edited 2006-12-06 00:09:41]

[Edited 2006-12-06 00:11:07]
 
miamiair
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RE: An XB-70 AV-2 Question.

Wed Dec 06, 2006 9:29 am

Might be a fairing for some hydraulic tubing. This is just a guess. I'll look in a book I have at my office tomorrow on the XB-70 project.
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2H4
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RE: An XB-70 AV-2 Question.

Wed Dec 06, 2006 11:38 am



I'm heading over to the USAF museum in Dayton this week...I'll look to see whether their XB-70 has the same fairing....


2H4


Intentionally Left Blank
 
Curmudgeon
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RE: An XB-70 AV-2 Question.

Wed Dec 06, 2006 12:09 pm

Interesting...I've learned a lot since I saw the XB-70 at Dayton back in 1974, and I forgot that it had such a severe angle joining the wing and nacelle structure. I wonder if that fairing was added to compare the airflow disturbance between the two sides of the aircraft?

Cur.
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Starglider
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RE: An XB-70 AV-2 Question.

Wed Dec 06, 2006 8:59 pm

Quoting Miamiair (Reply 1):
Might be a fairing for some hydraulic tubing. This is just a guess. I'll look in a book I have at my office tomorrow on the XB-70 project.

Thanks for checking. I have just about every book published about the aircraft but the fairing has never been described in any of the books i have. Hopefully yours sheds some light on this.

Quoting 2H4 (Reply 2):
I'm heading over to the USAF museum in Dayton this week...I'll look to see whether their XB-70 has the same fairing....

Looking forward to your findings, although i've never seen this fairing on AV-1 on any of the pictures published. It is one of my wishes to go and see the aircraft some time in the near future. Last time i was in Dayton was in 1968 and the XB-70 was still flying in those days, missed it by about 6 months as it arrived there in February 1969.

Quoting Curmudgeon (Reply 3):
I forgot that it had such a severe angle joining the wing and nacelle structure. I wonder if that fairing was added to compare the airflow disturbance between the two sides of the aircraft?

AV-1 has 0 degree dihedral. AV-2 had a 5 degree dihedral due to lessons learned from AV-1's instability at cruising speed and they corrected it on AV-2 by placing a 5 degree wedge between the inner wing/fuselage and main outer-wing during production before wing mating. I wonder, if your theory is true about the fairing, what effect the fairing had on the aircraft's trim at a cruising speed of M 3. It must have had some influence on how the supersonic shock-waves bounced of differently between left and right side? Undoubtedly the fairing housed some kind of test equipment but what is a mystery to me.

Thanks for your efforts so far.

Regards, Starglider.
 
miamiair
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RE: An XB-70 AV-2 Question.

Wed Dec 06, 2006 9:01 pm

Quoting 2H4 (Reply 2):
I'm heading over to the USAF museum in Dayton this week...I'll look to see whether their XB-70 has the same fairing....

AV2 and AV1 had numerous structural differences.

The pictures I have of AV1 arriving at Wright-Pat do not show this fairing on the right side.

Book did not have anything in it regarding this fairing.
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Curmudgeon
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RE: An XB-70 AV-2 Question.

Wed Dec 06, 2006 9:21 pm

Quoting Starglider (Reply 4):
It must have had some influence on how the supersonic shock-waves bounced of differently between left and right side?

Even subsonic cruise would have been adversely affected (it appears to my modern eyes) by the lack of fairing at the wing/body join. unfaired wings have high drag, and often unpredictable airflow characteristics due to interference between the two surfaces. A well designed fairing tends to blend the two distinct boundary layers and tame all of that nastiness.

I can't recall all the details of the projected B-70 mission profile, but I'd guess that the majority of the flight time would have been subsonic, with a Mach 3 dash to the weapon release point. That aircraft still seems to me to be the pinnacle of the art, if not the science, of aviation.
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Starglider
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RE: An XB-70 AV-2 Question.

Thu Dec 07, 2006 5:54 am

Quoting Curmudgeon (Reply 6):
A well designed fairing tends to blend the two distinct boundary layers and tame all of that nastiness.

The lack of fairing in the basic design of the XB-70 at the wing/fuselage joint serves a purpose: compression lift. This made the NAA XB-70 design win the contract over the competing Boeing design. In a nutshell, the wedge shape of the engine compartment was designed to interact with the lower wing surface to "trap" the supersonic flow and make use of the pressure increase that occurred as the shock waves bounced off the airframe at an oblique angle between engine compartment and lower wing surface. Since this phenomena only occurred on the lower side of the wing (the upper wing surface had a relatively undisturbed airflow) a considerable increase in lift (e.g. reduction in drag) was generated when compared to a conventional delta wing.

Quoting Curmudgeon (Reply 6):
I'd guess that the majority of the flight time would have been subsonic, with a Mach 3 dash to the weapon release point.

What you refer to is the original set of requirements from the mid 1950's before compression lift features were introduced into the design.

The beauty of the XB-70 as it exists today is that it was designed to cruise at Mach 3 / 70.000 + ft. There it was in it's element. If it would have seen service with USAF/SAC it would, after reaching TOC (Top Of Climb), have cruised at M.3 all the way to the target and back until reaching TOD (Top Of Descent) approaching home base (or a tanker). Apart from the materials used in it's construction to handle the heat, this was mainly achieved by the above-mentioned compression lift and it's engines that, combined with the "tailored" air intake design, produced the required thrust against the lowest possible fuel consumption for that flight regime. Even if 1 of it's 6 engines were to fail during a mission, it was advised to maintain above-mentioned speed and altitude over a lower speed/altitude to squeeze the maximum possible range out of that configuration.
 
Starglider
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RE: An XB-70 AV-2 Question.

Thu Dec 07, 2006 6:21 am

Quoting Miamiair (Reply 5):
AV2 and AV1 had numerous structural differences.

The pictures I have of AV1 arriving at Wright-Pat do not show this fairing on the right side.

Book did not have anything in it regarding this fairing.

Indeed, AV2 was a far superior aircraft compared to AV1. Mostly due to finding solutions to problems encountered manufacturing and flying AV1.

Thanks again for searching through the book you have. None of my books mention it either. I would have expected at least a reference to it in one of them because to me it's such a distinct feature of AV-2. Perhaps because it caught my attention when years ago i built a 1/72 scale model of AV-2 from scratch, based on requested and received drawings from North American Aviation at the time. It took me about 5 years to complete so perhaps that's why all the specific details of this aircraft are etched into my memory cells.
 
Blackbird
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RE: An XB-70 AV-2 Question.

Thu Dec 07, 2006 9:27 am

In regards to the differences between the XB-70 (A/V-1) and XB-70 (AV-2), the original A/V-1's hydraulic lines were fixed and not flexible, resulting in a number of leaks. The wing featured a mostly neutral wing (some anhedral was present at the wing-body junction), and the plane featured a manual only inlet control system. The metal skin featured a number of defects resulting in it being limited to a lower speed. The radome under the nose was also painted white.

AV-2 featured flexible hydraulic-lines, it's wings featured 5-degrees dihedral, the folding-tips folded an extra five degrees in the mid-position and the maximum position. The inlet control system was automatic, with manual override. The metallic skin was developed with experience learned from AV-1. As a result, far less if any problems occured with AV-1. The radome under the nose of A/V-2 was black instead of white, being one of the easiest ways to identify the two.

Their tail numbers are also different as well. AV-1 was designated 62-0001, which was written out as 20001 on the tail. AV-2 was designated 62-0207, which was writen out as 20207.

A commonly mistaken fact is that the XB-70 is capable of only Mach 3.0. In a respected book about the XB-70, plus an article written on a NASA website regarding the XB-70's inlets, indicate a much higher speed.

The book states that the X-279E (YJ-93) was rated for Mach 4 performance. The competitor as well, the Boeing 804-4 was designed additionally for Mach 4.0 performance. Considering that the XB-70 won, I doubt even with extra bomb-capacity and a better L/D ratio that it would have won with only Mach 3-speed. The high-speed capability was highly important!

The NASA site discussed an inlet design they tested on the XB-70, that would have produced a ninety-percent effciency at Mach 3.8. NASA would have no reason to overrate the speed of the XB-70 (especially since normally 3.0 is the listed figure) to such an extent, but they might have had a reason to under-rate it. After all it would be pretty amazing to know that even in the late fifties we had jet-enignes that could cruise (well continuously dash) at mach 4.

Considering the two of them do appear to be worthy of trust. It would be logical to conclude that the XB-70's cruise-speed would be either Mach 3.8 to Mach 4. Considering that the plane's likely cruise speed is Mach 4, or close too, I'd assume it would cruise at a considerably higher altitude than 75,000 feet.

Regarding the jet engine issue, the X-279E/J-93, and it's competitor, the J-91, which was known as the JT-9 (dunno if it's related significantly to the JT-9D) was also capable of similar speed. It featured a lower pressure ratio (7:1) since it didn't feature the advanced air-cooling system the J-93 featured. To compensate, the engine was bigger in diameter than the J-93. Since the J-93 ultimately was considerably more advanced, it won the competition. However before this happened, the Navy was in need of a high-mach engine to power an interceptor design of theirs, which I've been told was either an F-8U-III variant, or an advanced version of the A-3J (Later A-5 Vigilante), Pratt 'n Whitney developed an 80% scale version of the J-91 which was designated J-58. (To provide the smaller engine with rivalable power, they designed it with a variable inlet-guide vane to allow the blades to operate at a higher alpha and thus produce a higher PR, and once the compressor inlet temp rose past a given point, the guide-would shift to lower the alpha, reducing the pressure ratio to a lowever value. Allegedly it's thrust was around 26,500 lbf dry, and 45,000 lbf wet.). During the Valkyrie's development, they did sometimes consider using the J-58 as a back-up choice should the J-93 for one reason or another fail. For this reason, it is logical to assume the J-58 had around the same thrust and same top speed as the J-93 (M=4.0).

This fact also makes it fairly obvious that the A-12/YF-12A/SR-71 are obviously faster than Mach 3.2, or Mach 4.0, since the engines were heavily modified from their original capabilities.

Sincerely,
Andrea K
 
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RE: An XB-70 AV-2 Question.

Thu Dec 07, 2006 1:21 pm

Andrea, you'll be happy to know my SR-71 manual clearly indicates the SR was capable of exceding M3.2. My favorite page says "speeds greater than M3.2 must be approved by the Ops Group Commander".
I fly really fast and take a lot of chances.
 
miamiair
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RE: An XB-70 AV-2 Question.

Thu Dec 07, 2006 8:31 pm

Quoting Blackbird (Reply 9):
This fact also makes it fairly obvious that the A-12/YF-12A/SR-71 are obviously faster than Mach 3.2, or Mach 4.0, since the engines were heavily modified from their original capabilities.

SR-71 was not limited by M number, but by temperature.
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Curmudgeon
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RE: An XB-70 AV-2 Question.

Thu Dec 07, 2006 8:58 pm

Quoting Curmudgeon (Reply 3):
I've learned a lot since I saw the XB-70 at Dayton back in 1974



Quoting Starglider (Reply 7):
The lack of fairing in the basic design of the XB-70 at the wing/fuselage joint serves a purpose: compression lift

Thanks for the explanation. Turns out that I knew bupkis about the compression lift and the advantages of an unfaired wing/nacelle configuration.

As well as forgetting the compression lift effect, I also can't recall now why the program was cancelled. Was it missiles, cost, what? Between the XB-70 and the Avro Arrow there was an astonishing amount of design talent and insight that was wasted with the cancellations.
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RE: An XB-70 AV-2 Question.

Thu Dec 07, 2006 9:38 pm

Quoting Curmudgeon (Reply 12):
As well as forgetting the compression lift effect, I also can't recall now why the program was cancelled. Was it missiles, cost, what? Between the XB-70 and the Avro Arrow there was an astonishing amount of design talent and insight that was wasted with the cancellations.

Not to mention to TSR-2.

Wasn't it because ballistic missiles were becoming more precise?
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Blackbird
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 12:33 am

Quoting Rsbj (Reply 10):

The SR-71 manual that was published from what I read appeared to be largely loaded with misinformation. The mach numbers for example listed for it's top speed and cruise and such.

Considering the XB-70's J-93s were able to cruise on afterburner at Mach 4, considering all the modifications made to the J-58 (which originally had virtually the same speed capabilities) The J-58 used on the A-12 featured an engine-trim setting which leaned the fuel/air ratio out, and a de-rich setting for the burner to aid in fuel-consumption and AB temp. The engine also most notably featured a bleed-bypass system that could dump up to sixty-five percent (I think) of the airflow around the engine into the burner. The blade-geometry, and airflow-levels were increased as well, and air-cooling dramatically increased. There were other modifications as well. But the bulk of them were basically to keep the turbine temperature in check even though the plane was to go faster.

To be honest, the J-58 used on the A-12/SR-71 could have probably allowed for a cruise and dash speed higher than Mach 4 due to all the mods. Probably was capable of Mach 5 flight. The A-12 was faster than the SR-71 to my knowledge, although I have no idea as to how much.

Keep in mind, this plane outran missiles.

Let's hope I don't get a heart-attack folks! :p
Andrea K
 
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 3:00 am

Daaaaaaaamn this is some interesting stuff, keep it coming folks. Now I shall need to go visit the annex at the AF Museum while I am back in Cincy here in a week, and take a good long look at AV-1. I was about 6 or 7 the last time I saw that plane, I just recall it was bogglingly huge to my second-grade mind.

Blackbird, where do you get this stuff? Amazing.

-Meister
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grandtheftaero
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 4:52 am

Quoting Blackbird (Reply 9):
an article written on a NASA website regarding the XB-70's inlets

Blackbird, great info. Got a link?
 
Starglider
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 6:59 am

Quoting Blackbird (Reply 9):
A commonly mistaken fact is that the XB-70 is capable of only Mach 3.0. In a respected book about the XB-70, plus an article written on a NASA website regarding the XB-70's inlets, indicate a much higher speed.

Andrea,

Thanks for your informative contribution to this thread.

Indeed, the potential of the XB-70 was never fully explored during flight test. Engine design, intake (+ AICS), and airframe were capable of handling Mach 4 according to NAA. The engines (as installed) were cleared to a maximum of 95.000ft. For instance, as i explained earlier, NAA calculations showed that even with one J-93 shut down, the XB-70 could still maintain Mach 3 cruise with only a seven percent loss in range. This essentially is an indication that even as a prototype, the aircraft had thrust to spare. However to extend the limit to Mach 4, major revisions in the B-70's environmental control system and hydraulic fluid system would have been required.

By the way, does your information shed any light to my initial question regarding the fairing installed at the RH wing-root on AV-2? The closest i got is that AV-3 (partially built but never finished) would have been used to gather more test data to investigate heat buildup at the boundary layer intersection (in that specific wing-root area).

Regards,
Starglider
 
Starglider
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 7:32 am

Quoting Starlionblue (Reply 13):
Wasn't it because ballistic missiles were becoming more precise?

Partially true but the argument up to this day remains that a manned bomber can be recalled, missiles cannot. They didn't start to re-count from B-1 and up all over again for nothing. Political power-play killed the B-70 program as politics probably also saw to it that the investigation into the AV-2 crash was finished faster than the aircraft could fly. Apparently the thought of the day was to close the book as soon as possible and bury it till stories go hazy.

The Arrow and TSR-2 essentially met their fate the same way.

If technology would have prevailed i bet the B-70, Avro Arrow and TSR-2 would have been "three of a perfect pair".
 
Blackbird
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 7:57 am

Grand Theft-Auto,

To my knowledge, it was a NASA website. Try a google search for "Mach 3.8"+"XB-70"

In regards to the book where it said the X-279E's engine was rated for Mach 4 was Aero Series: North American XB-70 Valkyrie (Vol. 30) by Steve Pace. The specific comment was written on page six (second side of the page, around 60% down).


To Starglider,

Are you serious? The XB-70 never reached it's design speed? I find that hard to believe. If I recall correctly when Al White said "there's that big magic number" I assume he meant the planes operating cruise speed.

I actually don't know if it's true that the hydraulic systems needed any modifications. In regards to the environmental systems, the modifications were needed to my knowledge to allow 4 crew members instead of the prototypes' two man crew.

Andrea K

[Edited 2006-12-08 00:16:11]

[Edited 2006-12-08 00:16:44]
 
miamiair
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 8:02 am

Quoting Miamiair (Reply 11):
SR-71 was not limited by M number, but by temperature.

Here's the numbers I dug up:

The maximum scheduled speed was M3.17
Design number was M3.2
M3.3 could be flown when authorized by the detachment CO. Limited to a CIT (Compressor inlet temp) of 427C. M3.3 could not be exceeded, but the CIT of 450 for one hour could be used as a tactical limit.

One problem of flying faster than M3.3 would be if one of the engines would "unstart." The yaw would exert loads the fuselage was incapable of handling.
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 8:18 am

Quoting Blackbird (Reply 14):
Keep in mind, this plane outran missiles.

Let's hope I don't get a heart-attack folks! :p
Andrea K

The SR-71 was designed to outrun missiles. The United States got busted flying U-2s over the U.S.S.R. when one was shot down in 1960, carrying a payload of photos of "areas of interest" [oops].

At the time of the U-2, missiles could not reach its cruising altitude of ~FL650. However, the Soviets progressed in their development of missiles, until they could reach that altitude. After the "embarrassing mishap," the USA decided to go with altitude and speed.

I remember seeing a documentary on T.V. about this, interviewing both former US and Soviet officials. The Soviets stated something along the lines of "they knew something was up there...and they knew it was American, but they could never shoot it down, because it was too fast for missiles and their own aircraft."

This was enough to give the Soviets a heart-attack!   

Edited for grammar

[Edited 2006-12-08 00:21:13]
 
Blackbird
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 8:29 am

Look the J-58 prior to it being configured for bleed-bypass operation (and various other modifications that are beyond the scope) was capable of the same speeds as the J-93, which was Mach 4. The modifications only appear to be designed to make the plane capable of operating at speeds HIGHER than it's original capabilities.

In regards to the unstart issue, that is related to the INLET not the engine. It's a result of the shockwave getting expulsed from the inlet. The problem generally has to do with the inlet not being in the right position for the given mach number range. There would be no point to take an engine capable of doing mach 4, and then modifying it to go even faster, making a nearly all titanium airplane, using special fuel to tolerate all this heat, and then putting an inlet on the design that would max out at only Mach 3.3

Andrea K
 
miamiair
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 8:35 am

Quoting Blackbird (Reply 22):
In regards to the unstart issue, that is related to the INLET not the engine

Correct, but at operational speeds, the majority of the thrust came from the inlet, not the engine.
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Blackbird
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 8:40 am

To my knowledge, the inlet "produces thrust" in the fact that it dramatically increases pressure through ram-compression, so that the engine produces more power. The nozzle "produces thrust" because it properly sets the proper nozzle-area so the exhaust expands optimally.

In either case, modifying a mach 4 engine, for even higher speed, then designing an inlet that is designed for a lower speed then the engines prior to the mods is ludicris
 
Starglider
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 10:35 am

Quoting Blackbird (Reply 19):
To Starglider,

Are you serious? The XB-70 never reached it's design speed? I find that hard to believe. If I recall correctly when Al White said "there's that big magic number" I assume he meant the planes operating cruise speed.

I actually don't know if it's true that the hydraulic systems needed any modifications. In regards to the environmental systems, the modifications were needed to my knowledge to allow 4 crew members instead of the prototypes' two man crew.

The XB-70 met it's design speed/goals for the program as planned for the 2 prototypes. Al white called the "magic number" when reaching M3 for the first time in AV-1 but only for a few minutes. AV-1 was soon there-after limited to a M 2.5 machine because it started to shed it's skin panels. AV-2 (of improved design through lessons learned from AV-1) flew 32 minutes at M3+, long enough to demonstrate that the airframe and systems were heat stabilized (heat-soaked). This means that it demonstrated it's designed cruising speed (for M3 anyway) and that the encountered temperatures would remain stable. Meaning that if it were to cruise for 2 or 3 hours, which it could but never did, the thermal conditions for the airframe and systems would remain the same at that speed.

I wrote that the potential of the XB-70 design was never fully explored. If that were the case at least AV-3 would have been built and flown. Perhaps if the program had not been reduced to just 2 prototypes, who knows they might have explored higher speeds. And yes, AV-3 would have had a higher capacity ECS to allow 4 crew members and not to forget for added avionics and weapon systems that were to be incorporated in it and tested. It would also have had additional fuel stored in the folding wing tips, increasing it's range and have air refueling capability.

What i mean (apart from AV-3) is that North American Aviation claimed that the design was capable of Mach 4 flight but for that to happen (due to higher temperatures at M4) it needed to modify the ECS even further, same goes for the hydraulics as fluid temperatures and seals would also be affected.

Quoting Blackbird (Reply 24):
To my knowledge, the inlet "produces thrust" in the fact that it dramatically increases pressure through ram-compression, so that the engine produces more power. The nozzle "produces thrust" because it properly sets the proper nozzle-area so the exhaust expands optimally.

Here are the numbers, quoting from Space/Aeronautics May 1967"; article - "Inlets for Supersonic Aircraft":

Propulsion efficiency is fine tuning the combination of air intake, engine and exhaust nozzle. Understanding how to optimize supersonic-inlet shock patterns begins with understanding the increasing importance, as aircraft velocities increase, of the inlet's function as a compressor. In the high subsonic regime, the jet-engine compressor contributes 5 times as much pressure as the inlet; at M1.2, the inlet and engine contribute equivalent pressure rises to the airflow; but above M2.8 the engine contribution to pressure becomes negligible, and the inlet is running a compression ratio of approx. 40:1. These figures do not fairly reflect relative contributions to thrust, since power-plant thrust is produced by both pressure and temperature increases. Giving the heat rise contributed by the engine combustor its due, the portion of thrust provided by intake, engine and nozzle are about 60, 25 and 15 percent respectively at M3.

Regards,
Starglider
 
Curmudgeon
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 9:18 pm

I find this stuff fascinating, thank you for the information. Does anybody have any insights into supersonic bomber weapon launch speeds? I know the XB-70 test program stopped far short of that point, but in general I wonder if bombs/missiles can be launched at > M 1.0 given the complexities of opening bomb bays and introducing another object into the airstream?
Jets are for kids
 
xv408
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 11:27 pm

A technicality, but stating the engines are cleared to M3 or M4 is a bit of a misnomer. The engines do NOT like to run in supersonic air. The intakes slow the air down to around 300-400 mph by the front face of the engine (military and civil alike). The presure recovery of the intake is substantial, as noted by Starglider. The engine is almost reduced to being a pump. The limitation, as noted above, is inlet temperature, which is linked to turbine temperature which will be the limiting factor.
The J-58, by having a significant ammount of air bypassing the core of the engine at high speed, is heading towards being a ramjet, which is the most efficient form of propulsion at M3+.
 
Blackbird
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RE: An XB-70 AV-2 Question.

Fri Dec 08, 2006 11:36 pm

Starglider,

For some reason, I have trouble believing that they would go to such lengths to build a Mach 4 airplane and never get even close to that speed. The compression lift wouldn't have been anywhere near as effective at Mach 3 as Mach 4. As said, it would be better off to increase power on the remaining five engines, if one engine failed because of the dramatic gain in performance. It's temperatures would have been far lower than at Mach 3 as well.

To my knowledge, the purpose of A/V-3 was not to achieve Mach 4, but to actually demonstrate it's ability to release bombs, carry a crew of four with an improved environmental control system to provide cool pressurized air to four men instead of two. The plane would have featured a larger set of bomb-bays to carry 50,000 pounds of bombs, or a single large 40,000 pound bay. The plane would have been fitted with a mid-air refuelling receptacle, and fuel in the wing-tips to increase range. The plane would feature a new thermal-coat (it would alter the frequency of the energy produced by kinetic heating at frequencies that most IRST's the soviets had couldn't detect) for testing-- the coating would have been an opaque silver color by the way, not the traditional white. The plane would feature a new, larger canard (with a 51-degre sweep instead of a 31-degree leading edge) the nose-ramp may have been shaped slightly differently as well.


To Curmudgeon,

Releasing a weapon past Mach 1 is do-able. The F-102's and F-106's did it all the time. They both could exceed mach 2.

The XB-70 doors did not open in the usual sense. The doors slid aft, and the weapon was tossed off. There were two bays which allowed for up to 35,000 pounds of bombs on an arrangement like AV-1 and -2. A production model would have carried 50,000 in two bays. However I've been told they may have used one huge bay which would carry 40,000 pounds, or could carry an air-launched ballistic missile. Weapons release speeds would probably be around Mach 4.

Andrea
 
Starglider
Topic Author
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RE: An XB-70 AV-2 Question.

Sat Dec 09, 2006 9:05 am

Quoting Blackbird (Reply 28):
Starglider,

For some reason, I have trouble believing that they would go to such lengths to build a Mach 4 airplane and never get even close to that speed.

The goal for the XB-70 program in it's final form was to demonstrate that a 500.000 lb frame could sustain M3 cruise at 70.000 ft. Remember, it was a project that had initially started as a full production program to develop and build a B-52 successor but was eventually stripped down to an experimental project. True it remained a project "to boldly go where no one had gone before" . . . .but at a limited price tag. The experimental project thus had a limited budget and a limited goal to explore the feasibility of M3 flight for a 500.000 lb aircraft. It is obvious that, because the project was pioneering into yet to be explored territory, the XB-70 was designed conservatively, e.g. overdesigned for it's goal to achieve M 3. This plane was designed with slide rulers, not with super computers. Remember also that designing and engineering an aircraft has certain criteria to adhere to. Namely calculation of weight, temperatures, normal load, limit load (a load the aircraft may encounter maybe once or twice in it's lifetime) and ultimate load (usually a factor of 1.5 times limit load). My guess is that the plane was engineered for M3 but because of the unknowns ended up with growth potential for M4 as a bonus due to conservative calculations.

Quoting Blackbird (Reply 28):
The compression lift wouldn't have been anywhere near as effective at Mach 3 as Mach 4.

I will try to explain a complicated matter as aerodynamics as applied to the XB-70 in a nutshell:

Just because the airframe and it's engines (indeed, engines cannot digest supersonic flow very well as Xv408 explained) could possibly take the heat of a M4 environment does not automatically mean the same for it's aerodynamics. The aerodynamic shape of the wing and fuselage were specifically designed for Mach 3 cruise. The sweep angle of the wing leading edge was determined to cater for a M3 shock wave which was to contribute to compression lift. The angle of the shock wave at mach 3 precisely determined how compression lift would take effect on the center of lift on the wing. At supersonic speeds, with increasing speed, the center of lift shifts further aft relative to the center of gravity. There is a limit this center of lift is allowed to move otherwise drag would increase to unacceptable limits due to increased flight control deflection for trimming. Furthermore, apart from drag, as speed increases further the plane could reach it's trim limit and become unstable. At M4 the shockwaves will have a much sharper angle than at M3, resulting in a totally different flow pattern of the shockwaves and their interaction between wing and fuselage. Maybe to such an extent rendering it totally ineffective for use as compression lift.

Quoting Blackbird (Reply 28):
To my knowledge, the purpose of A/V-3 was not to achieve Mach 4

I never said it was. Essentially i said perhaps if the program was extended beyond the 2 prototypes. . . .who knows they might have explored higher speeds . . . not necessarily up to M4.

Quoting Blackbird (Reply 28):
As said, it would be better off to increase power on the remaining five engines, if one engine failed because of the dramatic gain in performance. It's temperatures would have been far lower than at Mach 3 as well.

Please explain a bit more about what you are trying to say here. Especially the sentence: "It's temperatures would have been far lower than at Mach 3 as well." does not touch wood with me.
 
2H4
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RE: An XB-70 AV-2 Question.

Sat Dec 09, 2006 10:43 am



Any last-minute photo requests before I head up to the USAF museum tomorrow?


2H4


Intentionally Left Blank
 
Blackbird
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RE: An XB-70 AV-2 Question.

Sat Dec 09, 2006 11:25 am

Starglider,

No, the XB-70 was not designed to show that a 500,000 pound plane could do Mach 3 at 70,000 feet. It was designed to replace the B-52. It was to carry at least 25,000 pounds of bombs, have a shirt-sleeve environment for it's crew and have ejection capsules to provide safe ejection at high-altitude and high speeds, and be able to use already existant SAC runways, and maintenance facilities. That was what it was designed to do. Both it and it's competitor were designed for Mach 4, to be powered by a J-91 or a J-93 with HEF-3/JP-4 in the burners. The XB-70 won the aircraft contract, and the J-93 won the engine contract. The HEF-3 was found to be impracticle and was eliminated, the wings and canards were made sharper, wing-body blending improved, a nose-ramp and moveable inlets added, with the canard changing into an all moving stab-trim still retaining the canard flap, additionally, the folding-wing-area increased, which allowed better directional stability and a smaller vertical stabilizer, saving weight, and to allow large deflection for engine failures, the surfaces were now redesigned into all-moving stabilizers. Additionally, the elevons were shortened spanwise and lengthened chord-wise and split into thin "finger"-like surfaces.

Let's play the game, and assume it was designed for Mach 4, the splitter's shockwave would not be totally under the wing, it would be under parts of the wing, but not all of it as it would at Mach 4.

The shape and thickness of wings, fuselage nose-angles, and wedge-splitter's angles determine the shockwave angles and strengths and such. The shape of the fuselage, and wing LE sweep angles, conical cambers, wedge-splitters and inlet ramps would not have been computed out so extensively just to build a plane that was capable of Mach 3 when the actual production model was meant for Mach 4. It would take too much time and effort to re-design everything. And the prototype and production models would require so much changes and modifications and re-designs, that it would have been better to simply design it from day one to do Mach 4, which seems to be the case.

When I said, the A/V-3's role was never to achieve Mach 4, I meant regarding how you said AV-1 and -2 could only achieve Mach 3, and AV-3 was designed for full-capability in terms of speed. I was trying to say that the purpose of A/V-3 was to test it's capabilities as a bomber, as a weapons system. I was however not stating that Mach 4 performance was still out of bounds. I was assuming it was already within the capabilities of the design; I was saying that A/V-2 could fly, or could have flown at Mach 4 already. A/V-3 definetly to my knowledge would have been able to do the job.

Andrea Kamarov
 
rsbj
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RE: An XB-70 AV-2 Question.

Sat Dec 09, 2006 4:48 pm

Just to clarify, I have the authentic manual, not a copy.
I fly really fast and take a lot of chances.
 
Starglider
Topic Author
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RE: An XB-70 AV-2 Question.

Sat Dec 09, 2006 7:33 pm

Quoting 2H4 (Reply 30):
Any last-minute photo requests before I head up to the USAF museum tomorrow?

Thank you so kindly for the offer. Íf it would be possible:
- The wing root (reason i started this thread);
- the black magnesium-thorium fairings covering the wing fold hinge line;
- the interiors of the wheel bays;
- variable geometry windshield and ramp (if in the lowspeed config.).


Regards,
Starglider
 
Starglider
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RE: An XB-70 AV-2 Question.

Sat Dec 09, 2006 7:55 pm

Quoting RSBJ (Reply 32):
Just to clarify, I have the authentic manual, not a copy.

Hmm, very interesting. I'm curious about what Section V: Operating Limitations; Section VI: Flight Characteristics; and Appendix I: Performance Data have to say regarding Vmo/Mmo. By chance, do you have Supplement T.O. 1B-70(X)A-1A? Because that's where flight characteristics and performance data were to be found according to the copy of the manual i have. My copy does not have that information. Neither does it have the operating limitations section.
 
Blackbird
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 12:56 am

RSBJ, how do you know it's an authentic manual? And, if you can, what are the performance listings?
 
rsbj
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 1:16 am

I'm on a trip now, when I get home next week I'll get it out. To verify it's authenticity, I had an SR pilot look it over.
I didn't realise copies of the manual existed. Are they fairly comprehensive? Do they have the speed and altitude charts?
Thanks,
Rick
I fly really fast and take a lot of chances.
 
Starglider
Topic Author
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 2:17 am

Quoting Rsbj (Reply 36):
I'm on a trip now, when I get home next week I'll get it out. To verify it's authenticity, I had an SR pilot look it over.
I didn't realise copies of the manual existed. Are they fairly comprehensive? Do they have the speed and altitude charts?
Thanks,
Rick

The manual i have ( T.O. 1B-70(X)A-1) consists of the sections:
- (Aircraft Systems) Description
- Normal Procedures
- Emergency Procedures

These sections are very comprehensive indeed. For the above 3 sections alone i had to split them into 2 separate standard flight manual binders.

The limitations, flight characteristics and performance sections were left out as the manual refers to the supplement i mentioned in my previous message. So unfortunately there are no speed and altitude charts illustrating limitations or performance in my manual.

The sections normal and emergency procedures do contain some charts, for instance referring to wingtip operation (altitude, IAS and Mach number) or engine air start envelope (altitude / Mach number).

The high end of the air start chart gives a reliable air start envelope for up-to 83.500ft at Mach 3. The max. altitude shown on this chart is 90.000ft and the max. Mach number shown is Mach 3.
 
HaveBlue
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 2:33 am

Starglider rsbj has an SR-71 manual, not an XB-70 manual. Thought that might clear up some confusion.
Here Here for Severe Clear!
 
SlamClick
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 3:08 am

Quoting Starglider (Reply 7):
The beauty of the XB-70 as it exists today is that it was designed to cruise at Mach 3 / 70.000 + ft.

I too disagree with this statement.

The beauty of the XB-70 is its beauty.

I've said this before; the XB-70 may be the most beautiful thing man ever made out of metal. The sight of one of them at about 10-12 thousand feet, over Monterey, turning back toward Muroc is one of those freeze-frame memories I cherish.

BTW: Does anyone know the best way to remove a fish hook from the Slammer's mouth?

I actually believed that Blackbird was a 16-20 year old female. I believed it through three or four posts, wondering: Who the hell IS this person?
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
Starglider
Topic Author
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 5:53 am

Quoting Blackbird (Reply 31):
Let's play the game, and assume it was designed for Mach 4, the splitter's shock-wave would not be totally under the wing, it would be under parts of the wing, but not all of it as it would at Mach 4.

Andrea,

Thanks again for your comprehensive explanation regarding the airplane's development.

I've been digging deeper in my documentation and found the aircraft's placard speed, or Vmo. This is 575 Knots IAS (nose ramp up). To obtain optimum performance, the aircraft will need to operate near this maximum placard speed for climb, cruise and descent but not above it because of DESIGN CONSIDERATIONS. Normally speed is stabilized 10 to 15 kts IAS or Mach 0.05 below this placard limit speed.

Now when we translate 575 Kts IAS (Vmo) to Mach number at 72.000 ft (standard day atmosphere) this would be a Mmo of somewhere between Mach 3.2 to Mach 3.4. Under these conditions it also reached the temperature limit of 630 F. for the structure (at some places near the engines 675-1000 F.) The majority of the B-70 structure must carry flight loads at a structural temperature of 475 F. Some areas of the inlet duct and leading edges reached temperatures as high as 630 F., while the internal structure in some engine compartment areas reached temperatures as high as 1000 F. through engine heat rejection. At these temperatures, the structure had to carry the loads produced by maneuvering and gusts, as well as those caused by the speed and weight of the aircraft.

The materials and their percentages (by weight) used for the structure are:

- AM 355 steel 4%: for small fittings and actuators.
- PH15-7 Mo steel 68%: for brazed honeycomb sandwich panels, frames.
- 4Al-3Mo-1V and 6Al-4V Titanium 9%: Mostly used in the forward fuselage.
- H11 tool steel 17%: Landing gear, frames.
- René 41 nickel base alloy 2%: Critical structures in the engine bay.

Summarizing the B-70 temperature development:
Structures: 450 - 630 F.
Fuels and oils: 300-450 F.
Electrical Systems: 550 F.
Hydraulic Systems: -65- 630 F.
Seals: 500-630 F.
Greases: 450 F.
Tires: 360 F.
Radomes and windows: 500-530 F.


A Mach 4 airframe would encounter temperatures of approx. 1300 to 1500 F (with the airframe in stabilized cruise conditions).
The XB-70 was not constructed with materials that met those requirements.

Regards,
Starglider
 
Starglider
Topic Author
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 6:15 am

Quoting HaveBlue (Reply 38):
Starglider rsbj has an SR-71 manual, not an XB-70 manual. Thought that might clear up some confusion.

HaveBlue,
Thanks for clearing this up. I guess i thought he did because he did not reply to any previous reply in his text.
 
Starglider
Topic Author
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 9:10 am

Quoting SlamClick (Reply 39):
The beauty of the XB-70 is its beauty.

I've said this before; the XB-70 may be the most beautiful thing man ever made out of metal.

True, even if you don't ask why . . .

Quoting SlamClick (Reply 39):
BTW: Does anyone know the best way to remove a fish hook from the Slammer's mouth?

Try the 'Lip Grip' Fish Landing Tool, it protects you and reduces the possibility of injury to the fish you are landing. It makes landing, hook removal, weighing, and releasing a safe and easy one-hand operation...
Once you have the fish at boat-side, simply slide the pinchers over the bottom jaw of the fish and pull up. The weight of the fish tightens the pinchers, securing the fish, without causing injury to it. Weight can be read from the scale on the side of the tool, and the fish can then be returned to the water and released by simply pulling back on the T-collar. Here is a picture:

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Quoting SlamClick (Reply 39):
I actually believed that Blackbird was a 16-20 year old female. I believed it through three or four posts, wondering: Who the hell IS this person?

Maybe someone who has been reading about the subject since she could read and continued to do so for at least 16 years of her life? Or maybe a blackbird year is longer . . . .
 
Blackbird
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 11:03 am

I'm 24 years old -- I just updated my bio.
 
2H4
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 1:21 pm



Ok, Starglider, here's what I was able to get.

The XB-70 now resides in the off-site R&D hangar. That hangar is located on secure government property....a bus shuttles visitors back and forth between the museum and the R&D hangar.

The cool part is the lighting. Because the hangar doors are glass, natural sunlight can filter through and illuminate the aircraft. I was in there at around 4pm today, so the sun was low on the horizon, and cast some nice light on the exhibits.

Click on any of these for large versions....

Here are some shots of the wing root:

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(I like this shot)




Here's a shot looking back at the flaps (or flaperons, or whatever they're called):

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Here's a shot of some kind of exhaust outlet just behind the nose gear:

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Here are some shots of the black wing hinge:

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Interestingly, there was a panel missing from the right-side hinge, so I was able to get some detailed internal shots for you. You can see the shaft upon which the wingtips pivot:

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And here are some shots of the windscreen:


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I was fortunate to have such nice lighting....a few years ago, when the XB-70 was in one of the main museum hangars, lighting like this would have been unheard of.




Here are some shots of the gear:

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I have other gear shots, but I don't have enough room in my profile allotment to post them here. Copy as many of these shots as you'd like. Let me know when you're done, and I'll post the rest of the gear shots.




Finally, when browsing through the archives, I found a shot of SlamClick, back in his feistier, more mischievous days:

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 Wink



Hope these help you out, Starglider.


2H4


Intentionally Left Blank
 
meister808
Posts: 924
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 5:06 pm

Good work, 2H4. Lots of interesting stuff on there.

Is that engine in the background of the first landing gear picture one of the ones out of this airplane? Looks like a beast, whatever it is.

-Meister
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
 
Curmudgeon
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 7:15 pm

Thanks 2H4, really appreciate it. Is it just me, or is it incredible that the B-36 was still flying only ten years before the -70?
Jets are for kids
 
Starglider
Topic Author
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 8:30 pm

Quoting 2H4 (Reply 44):
Hope these help you out, Starglider.


2H4

2H4,

WOW!! Thank you ever so much!! These are great shots.
So many details show that this kind of ultimate engineering rises above the magic of art!! Stuff stars are made of.

Seeing these images, i am planning to jump the pond this summer and visit her myself.

I have copied all of the images to my ever-growing XB-70 data base.

I shall also use this information to improve the details of the model i made of AV-2. Like art, it is never finished. I'll make some pictures of it soon and add them to my profile.


Thanks again,
Starglider
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 10:34 pm




Quoting Meister808 (Reply 45):
Is that engine in the background of the first landing gear picture one of the ones out of this airplane? Looks like a beast, whatever it is.

You know, I think it must be one of the XB-70s engines. To be perfectly honest, I don't recall ever even seeing that engine....I was too focused on the bird itself!  blush 

Quoting Curmudgeon (Reply 46):
Is it just me, or is it incredible that the B-36 was still flying only ten years before the -70?

I know what you mean. It's funny how technology overlaps. I was reminded of the progress in communication upon seeing a typewriter in the VC-137 (Air Force One).

Quoting Starglider (Reply 47):
Seeing these images, i am planning to jump the pond this summer and visit her myself.


Glad you liked the shots. If you're ever able to make the trip, plan on spending a couple days here, so you can see everything without feeling rushed.

Thanks for the compliments...I'll post those other gear shots in a few days.


2H4


Intentionally Left Blank
 
RichardPrice
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RE: An XB-70 AV-2 Question.

Sun Dec 10, 2006 11:18 pm

Quoting N231YE (Reply 21):
The Soviets stated something along the lines of "they knew something was up there...and they knew it was American, but they could never shoot it down, because it was too fast for missiles and their own aircraft."

I dont believe the SR71 ever carried out an overflight over the USSR.

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