Starglider From Netherlands, joined Sep 2006, 644 posts, RR: 45 Posted (7 years 1 week 1 day 15 hours ago) and read 7300 times:
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.
Curmudgeon From Australia, joined Oct 2006, 695 posts, RR: 22 Reply 3, posted (7 years 1 week 1 day 10 hours ago) and read 7234 times:
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?
Starglider From Netherlands, joined Sep 2006, 644 posts, RR: 45 Reply 4, posted (7 years 1 week 1 day 2 hours ago) and read 7195 times:
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.
Curmudgeon From Australia, joined Oct 2006, 695 posts, RR: 22 Reply 6, posted (7 years 1 week 1 day 1 hour ago) and read 7192 times:
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.
Starglider From Netherlands, joined Sep 2006, 644 posts, RR: 45 Reply 7, posted (7 years 1 week 17 hours ago) and read 7135 times:
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 From Netherlands, joined Sep 2006, 644 posts, RR: 45 Reply 8, posted (7 years 1 week 16 hours ago) and read 7122 times:
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 From , joined Dec 1969, posts, RR: Reply 9, posted (7 years 1 week 13 hours ago) and read 7089 times:
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.
Miamiair From , joined Dec 1969, posts, RR: Reply 11, posted (7 years 1 week 2 hours ago) and read 7046 times:
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.
Curmudgeon From Australia, joined Oct 2006, 695 posts, RR: 22 Reply 12, posted (7 years 1 week 2 hours ago) and read 7043 times:
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.
Starlionblue From Greenland, joined Feb 2004, 16358 posts, RR: 66 Reply 13, posted (7 years 1 week 1 hour ago) and read 7031 times:
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." - from Citadel by John Ringo
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
Meister808 From United States of America, joined Jan 2000, 973 posts, RR: 1 Reply 15, posted (7 years 6 days 20 hours ago) and read 7001 times:
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.
Twin Cessna 812 Victor, Minneapolis Center, we observe your operation in the immediate vicinity of extreme precipitation
Starglider From Netherlands, joined Sep 2006, 644 posts, RR: 45 Reply 17, posted (7 years 6 days 16 hours ago) and read 6965 times:
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.
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).
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 From , joined Dec 1969, posts, RR: Reply 19, posted (7 years 6 days 15 hours ago) and read 6943 times:
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).
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.
Miamiair From , joined Dec 1969, posts, RR: Reply 20, posted (7 years 6 days 15 hours ago) and read 6941 times:
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.
Let's hope I don't get a heart-attack folks! :p
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!
Blackbird From , joined Dec 1969, posts, RR: Reply 22, posted (7 years 6 days 14 hours ago) and read 6928 times:
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
Blackbird From , joined Dec 1969, posts, RR: Reply 24, posted (7 years 6 days 14 hours ago) and read 6921 times:
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
25 Starglider: 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 fi
26 Curmudgeon: I find this stuff fascinating, thank you for the information. Does anybody have any insights into supersonic bomber weapon launch speeds? I know the X
27 Xv408: 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
28 Blackbird: 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 s
29 Starglider: 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
30 2H4: Any last-minute photo requests before I head up to the USAF museum tomorrow? 2H4
31 Blackbird: 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
32 RSBJ: Just to clarify, I have the authentic manual, not a copy.
33 Starglider: 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 c
34 Starglider: Hmm, very interesting. I'm curious about what Section V: Operating Limitations; Section VI: Flight Characteristics; and Appendix I: Performance Data
35 Blackbird: RSBJ, how do you know it's an authentic manual? And, if you can, what are the performance listings?
36 Rsbj: 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
37 Starglider: The manual i have ( T.O. 1B-70(X)A-1) consists of the sections: - (Aircraft Systems) Description - Normal Procedures - Emergency Procedures These sec
38 HaveBlue: Starglider rsbj has an SR-71 manual, not an XB-70 manual. Thought that might clear up some confusion.
39 SlamClick: 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
40 Starglider: Andrea, Thanks again for your comprehensive explanation regarding the airplane's development. I've been digging deeper in my documentation and found
41 Starglider: HaveBlue, Thanks for clearing this up. I guess i thought he did because he did not reply to any previous reply in his text.
42 Starglider: True, even if you don't ask why . . . Try the 'Lip Grip' Fish Landing Tool, it protects you and reduces the possibility of injury to the fish you are
43 Blackbird: I'm 24 years old -- I just updated my bio.
44 2H4: 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
45 Meister808: 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 air
46 Curmudgeon: 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?
47 Starglider: 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!!
48 2H4: 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 t
49 RichardPrice: I dont believe the SR71 ever carried out an overflight over the USSR.
50 Starglider: You know, age is unimportant but the enthusiasm and the determination with which you share your thoughts in these threads are very much appreciated.