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transaeroyyz
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Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 3:28 am

Confirmed, birds and planes flying in V formation saves energy and fuel, brings the question, what about airlines going across the pond in formation, synchronize the auto pilots to identify each other and maintain distance, is it even close to fesable?
 
Speedbird741
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 3:50 am

There is an ongoing study of such fashion of flight being executed by the University of Cape Town, Airbus, and I believe by South African Airways as well to some extent. I believe these two links might be of interest to you and lead you onto further, more detailed information.

http://www.uct.ac.za/mondaypaper/?id=8382/

http://www.aeroafrica-eu.org/download/20101123_news.pdf

Speedbird741
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tdscanuck
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 3:51 am

Quoting transaeroyyz (Thread starter):
Confirmed, birds and planes flying in V formation saves energy and fuel

How was that a myth even in need of testing? It's basic aerodynamics.

Quoting transaeroyyz (Thread starter):
what about airlines going across the pond in formation, synchronize the auto pilots to identify each other and maintain distance, is it even close to fesable?

These guys think so:
http://ocw.mit.edu/courses/aeronauti...projects/apendix1prntabl1_prnt.pdf

The C-17 has been working on the formation flying technology required for many years. It's not really a technical hurdle, more of a certification/ATC issue.

Tom.
 
N243NW
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 5:51 am

Quoting tdscanuck (Reply 2):
How was that a myth even in need of testing? It's basic aerodynamics.

  I think Mythbusters is running out of real "myths" to test and has recently had to resort to testing scientific facts instead, just because they sound cool.
B-52s don't take off. They scare the ground away.
 
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Starlionblue
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 7:12 am

Quoting N243NW (Reply 3):
Quoting tdscanuck (Reply 2):
How was that a myth even in need of testing? It's basic aerodynamics.

  I think Mythbusters is running out of real "myths" to test and has recently had to resort to testing scientific facts instead, just because they sound cool.

Full disclosure: I am a big fan of the show. And yes, there are often basic physics being tested, such as the infamous airplane on a conveyor belt.

My comments on this kind of thing being tested:
1. I really don't think the Mythbusters themselves need any convincing if it is just "basic physics". You can often catch them playing a bit dumb, and Adam especially often has snarky comments about the whole thing ("unless we have somehow been transported to another planet, I doubt this will work." comes to mind).
2. The inquisitive general public (AKA the target audience) typically has little grasp of this kind of thing.

It's all well and good to sit here in tech_ops, but most people are both less than well educated and less than analytically minded. So let's cut the Mythbusters a bit of slack shall we?  
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
PapaChuck
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 12:48 pm

Mythbusters, while I love the show, is just like any other. Ratings are more important than true science. If it sounds cool and we can get more people to tune in, then let's do it!

Also, technical and ATC issues aside (which by themselves would kill the idea), would anyone really want to spend eight hours riding the wake of a 747?

"Hey center, how are you rides ahead? We're getting continuous moderate chop and some mountain wave."

"Your wingman says it's been smooth since wheels up."

PC
In-trail spacing is a team effort.
 
tdscanuck
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 2:48 pm

Quoting PapaChuck (Reply 5):
Also, technical and ATC issues aside (which by themselves would kill the idea), would anyone really want to spend eight hours riding the wake of a 747?

In order for the idea to work, you can't be inside the wake. You need to be in an area of smooth upwash, which has to be outboard of the trailing vortices. Away from the ground, the wake vortices tend to move together and stream aft and down about half a wingspan apart...if you're running into those, you're way outside the typical "V" formation.

Tom.
 
chimborazo
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 3:44 pm

Is it a flock of geese?

Is it Superman??

No! It's just the TATL airlines all together in the new V Alliance.
 
PapaChuck
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 5:04 pm

I understand that you would need to fly outside and above the core of the vortex to see any benefit at all, but would the upward flow of air be uniform over the 200 foot wingspan of a trailing aircraft? While not technically in the wake, I find it hard to believe that it would be a perfectly smooth ride, at least requiring constant control inputs to keep the wings level.

It reminds me of yet another Mythbusters experiment where they measured fuel consumption driving in the wake of a semi. While it did indeed save gas, the closer they got, the harder it became to accurately control the throttle to keep a constant distance and thus negated some of the benefit. They closer they got, the harder they had to work.

Common sense should tell me that riding the bumper of a semi at highway speeds with my two-year-old daughter strapped in behind me is a bad idea. Scale that up to 400 people in a 747 tailgating another widebody, this should have stupid written all over it. Where does the safety and well being of paying passengers come in to play?

PC
In-trail spacing is a team effort.
 
jetblueguy22
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 5:42 pm

I can see it now, the Ryanair flying V!
Blue
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skysurfer
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RE: Myth Busters: Flying V Formation Saves Fuel

Fri Jan 27, 2012 10:07 pm

What a great example of wake turbulence it was when they lined up astern of each other and were all over the sky trying to keep it lined up!
It would've been alot better though if they'd have measured each aircraft's fuel flow flying straight and level by themselves, then tested all of the aircraft in the V formation.

Stu
In the dark you can't see ugly, but you can feel fat
 
N243NW
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RE: Myth Busters: Flying V Formation Saves Fuel

Sat Jan 28, 2012 2:16 am

Quoting Starlionblue (Reply 4):
It's all well and good to sit here in tech_ops, but most people are both less than well educated and less than analytically minded. So let's cut the Mythbusters a bit of slack shall we?

I agree with everything you said. I enjoy the show as well, but I just figured it was worth mentioning...
B-52s don't take off. They scare the ground away.
 
tdscanuck
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RE: Myth Busters: Flying V Formation Saves Fuel

Sat Jan 28, 2012 2:34 am

Quoting PapaChuck (Reply 8):
I understand that you would need to fly outside and above the core of the vortex to see any benefit at all, but would the upward flow of air be uniform over the 200 foot wingspan of a trailing aircraft?

At the separations most studies seem to work with, it will be pretty uniform. Not 100%, of course, but not nearly as bad as you might think.

Quoting PapaChuck (Reply 8):
While not technically in the wake, I find it hard to believe that it would be a perfectly smooth ride, at least requiring constant control inputs to keep the wings level.

This whole idea really only applies in cruise and pretty much guarantees that it can only be done in autopilot, at which point constant control inputs aren't an issue. Smoothness is different...bumps come from shear. The only source of shear is the trailing vortex sheet, which rolls up to form the trailing vortices. You're way outside that in normal V-formation position...you're just in the bulk updraft from the aircraft which isn't totally uniform but contains almost no shear at all.

Quoting PapaChuck (Reply 8):
It reminds me of yet another Mythbusters experiment where they measured fuel consumption driving in the wake of a semi.

A semi has a square back end and throws huge alternating vertical vortices...it's pretty much the opposite of the wake off an airliner.

Quoting PapaChuck (Reply 8):
Scale that up to 400 people in a 747 tailgating another widebody, this should have stupid written all over it. Where does the safety and well being of paying passengers come in to play?

This idea doesn't work by tailgating...you're not behind or beside the other aircraft. You should be able to maneuver in any direction and not hit anyone unless you change speed. Since the whole concept relies on slaved autopilots it's really not that big a deal...if the system is working, stay in formation and you're fine. If it's not, descend and you're clear.

An ILS autoland is a way harder collision problem than this is.

Tom.
 
UAL747
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RE: Myth Busters: Flying V Formation Saves Fuel

Sat Jan 28, 2012 6:22 am

In reality, the airplanes all have to take off, then line up in formation meaning others have to circle and wait or fly incredibly slow while others fly incredibly fast, then once they near an airport, they must break off and separate for landing meaning they will have to circle once they reach their destinations. Seems that all fuel savings would be lost in this process and it's not economically feasible.

Also, from how I understand this works, the planes ride on each others vortexes, on the upward movement or "side" of the vortexes. This air is extremely turbulent, so it probably wouldn't work that way either.

UAL
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tdscanuck
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RE: Myth Busters: Flying V Formation Saves Fuel

Sat Jan 28, 2012 7:54 am

Quoting UAL747 (Reply 13):

In reality, the airplanes all have to take off, then line up in formation meaning others have to circle and wait or fly incredibly slow while others fly incredibly fast, then once they near an airport, they must break off and separate for landing meaning they will have to circle once they reach their destinations. Seems that all fuel savings would be lost in this process and it's not economically feasible.

You're assuming they all depart and arrive at the same airport...there's nothing wrong with, say, the DC flight to Europe picking up two or three flights of New York and Philly and one from Boston then all following the same NAT in formation until they get to Shannon or so, then breaking apart to their final destinations. If the fuel savings is bigger than the relatively small increase in route length, it works out economically.

Quoting UAL747 (Reply 13):
Also, from how I understand this works, the planes ride on each others vortexes, on the upward movement or "side" of the vortexes. This air is extremely turbulent, so it probably wouldn't work that way either.

It's only extremely turbulent near the vortex core where the shear is high...that's below and about half a semi-span inside the wing tips...not where your formation mates are flying. This is no different than photo-shoot or air show formations and they don't have a turbulence problem.

Tom.
 
Starglider
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RE: Myth Busters: Flying V Formation Saves Fuel

Sat Jan 28, 2012 8:27 am

Quoting UAL747 (Reply 13):
In reality, the airplanes all have to take off, then line up in formation meaning others have to circle and wait or fly incredibly slow while others fly incredibly fast, then once they near an airport, they must break off and separate for landing meaning they will have to circle once they reach their destinations. Seems that all fuel savings would be lost in this process and it's not economically feasible.

Then this is the time to start designing and building large seaplanes and seabases.
 
bellancacf
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Jan 29, 2012 4:22 am

I once saw a vee of cormorants pass overhead, followed by two stragglers. Straggler A was content to come in last and slotted onto the end of the near arm of the vee; wingbeats slowed by a good third. Straggler B was a more competitive sort and wanted to be near the head of the vee; when the vee passed out of sight, Straggler B was still working hard to catch the vee while flying straight up the middle --- harder than any of the other birds, in fact. Even the leader of the vee, which I found curious ... Is there any reason the lead bird/plane might find an advantage in having other birds/planes in the vortices?

Related: I once found that a hand-launched glider with squared (as in 90 degrees) wingtips and a slight sweep (15 degrees) flew __much__ farther and better than the same plane with wingtips parallel to the fuselage. Always assumed that it was because the trailing edge got out of the way of the downdraft side of the vortex as it moved forward. The planes would leave your hand, give a little shake, squat slightly, and go find a thermal. Took to writing my phone number on them.
 
tdscanuck
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Jan 29, 2012 5:02 am

Quoting bellancacf (Reply 16):
Is there any reason the lead bird/plane might find an advantage in having other birds/planes in the vortices?

Unless you're going supersonic, the rotation extends both in front of and behind the aircraft. It's not as pronounced in front but the lead aircraft is still getting some boost from the updraft outside his trailing neighbors.

Tom.
 
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Starlionblue
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Jan 29, 2012 7:09 am

Quoting tdscanuck (Reply 17):
Quoting bellancacf (Reply 16):
Is there any reason the lead bird/plane might find an advantage in having other birds/planes in the vortices?

Unless you're going supersonic, the rotation extends both in front of and behind the aircraft. It's not as pronounced in front but the lead aircraft is still getting some boost from the updraft outside his trailing neighbors.

In the case of ducks and other formation flying birds, the lead position is traded off regularly in order to ensure one bird does not carry the whole burden.

Shouldn't be too hard to program that in I guess.  
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
ferpe
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Jan 29, 2012 9:46 am

Quoting tdscanuck (Reply 14):
This is no different than photo-shoot or air show formations and they don't have a turbulence problem.

Oh yes they do, once you hit the vortex sheet the movement of your aircraft is pretty hefty even for a 15t fighter. That is why flying close formation is such an art of staying outside the lead aircrafts vortex or be prepared to counter with rather big stick movements if needed. If you were to see the stick of one of the trailing aircraft on those airshow formations you would see what hard work it is, no smooth sailing, BIG corrections, they fly so close they hit vortexes all the time. Those are the most difficult places in the formation for that reason.

For normal fighter pilots you get into the same situation when you fly formation in clouds, if they are dense you have to get to about 3-5 meters from the other frame not to loose him. Then you make very sure you stay out of his vortexes and if you hit them you correct razorfast and distinct to get out of them. No way you can fly in them.

Even when changing flanks trailing about 50-100 meter you go down a lot to not hit the vortex sheet. In flight academy you deliberately go up and hit it, you get roll disturbances of 30° for a Hawk style jet.


PS the above is just a correction of the thought that airshow style formation flying is smooth sailing, for the V form to work practically you stay outside these vortex sheets as said and there is good reasons for it DS

[Edited 2012-01-29 02:22:32]
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Geezer
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Feb 12, 2012 5:50 am

This very interesting discussion about turbulence from planes flying close together has reminded me of something I read about many years ago....................when the USAF was testing the XB-70 Valkyrie they always used at least one chase plane as an "observer"; on one fateful flight, the late Joe Walker was flying the F-104 Starfighter chase plane; something happened, and the F-104 collided with the B-70; the F-104 was lost, as was the pilot, and the XB-70 I believe ended up making a rather spectacular landing on a highway. ( There were only 2 copies of the B-70 made )

Does anyone here remember this, and if so, is it fair to speculate that wake turbulence had a hand in causing this tragedy?

It's been a long time since I read about this, but I do remember that there were many people (think "brass" ) in the USAF that were making all sorts of extremely unflattering comments about Joe Walker; ( who I believe was working for NASA, ( or possibly the old NACA ) at the time. I'm sure these comments upset more than a few people, as Joe Walker was considered to be among the top test pilots of the time.

I would love to hear some "educated" discussion about this incident.

Charley
Stupidity: Doing the same thing over and over again and expecting a different result; Albert Einstein
 
rwessel
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Feb 12, 2012 8:03 am

Quoting geezer (Reply 20):
This very interesting discussion about turbulence from planes flying close together has reminded me of something I read about many years ago....................when the USAF was testing the XB-70 Valkyrie they always used at least one chase plane as an "observer"; on one fateful flight, the late Joe Walker was flying the F-104 Starfighter chase plane; something happened, and the F-104 collided with the B-70; the F-104 was lost, as was the pilot, and the XB-70 I believe ended up making a rather spectacular landing on a highway. ( There were only 2 copies of the B-70 made )

The F-104 sheared of most of both vertical stabilizers on the XB-70, and did additional damage to the wing. The XB-70 remained in level flight for a few seconds after the collision, but then rolled inverted, entered a flat spin, had additional structural failures from the aerodynamics loads (the photos show a large could of fuel venting from the ruptured left wing), and finally impacted the desert floor. White ejected, but was very badly injured, Cross did not, and died in the accident. There was no landing.

Quoting geezer (Reply 20):
Does anyone here remember this, and if so, is it fair to speculate that wake turbulence had a hand in causing this tragedy?

It's been a long time since I read about this, but I do remember that there were many people (think "brass" ) in the USAF that were making all sorts of extremely unflattering comments about Joe Walker; ( who I believe was working for NASA, ( or possibly the old NACA ) at the time. I'm sure these comments upset more than a few people, as Joe Walker was considered to be among the top test pilots of the time.

I would love to hear some "educated" discussion about this incident.

While wake turbulence has been discussed, specifically the vortex off the right wingtip, the problem is that the effect is not usually severe enough to prevent the trailing aircraft from compensating, or maneuvering out of the wake, at least until you're *really* close. And on numerous prior flights chase planes had not noticed anything unusual as far as that was concerned.

While I don't think we'll ever know exactly what happened, the problem is that there were no apparent failures anywhere else. The telemetry from the XB-70 showed no abrupt motions or mechanical failures (until the collision), other pilots reported no (atmospheric) turbulence during the that time, and while it can't be ruled out, the odds of a mechanical or structural failure of the F-104 at that exact time are remote (and there was no evidence of any such in the wreckage), and the other pilots noted no unusual flying from either the XB-70 or the F-104.

So what does that leave? Walker was a highly experiences and well regarded pilot. Yet his F-104 hit the XB-70. Might he have suffered a medical problem? Hypoxia was theorized, but without evidence (and the apparently normal performance of the F-104 prior to the accident would suggest that Walker was not impaired). Perhaps distracted by something in the aircraft or outside (there was a B-58 crossing their path, although above them, just before the collision)? But would an experienced pilot let his attention drift during a close formation flight? And if he had an issue, the first thing to do would be to open the range, and *then* deal with the issue. And yet the F-104 managed a (fairly) slow drift into its lead aircraft, which is the sort of thing that happens when you get distracted.
 
Geezer
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Feb 12, 2012 5:46 pm

Quoting rwessel (Reply 21):
The F-104 sheared of most of both vertical stabilizers on the XB-70, and did additional damage to the wing. The XB-70 remained in level flight for a few seconds after the collision, but then rolled inverted, entered a flat spin, had additional structural failures from the aerodynamics loads (the photos show a large could of fuel venting from the ruptured left wing), and finally impacted the desert floor. White ejected, but was very badly injured, Cross did not, and died in the accident. There was no landing.

Thank you so much ! (Just goes to show how accurate my memory is ! ) Somewhere back in my memory, I could swear I read something about the XB-70 having some kind of emergency and ending up landing on a road.........

Inasmuch as the copy of the B-70 that I have seen many times at the Air Force Museum is still intact, I just "assumed" the other copy was the one involved in the road incident. ( Which incident, BTW, apparently involved another aircraft. )

My brother-in-law had worked in experimental engineering at Wright Field during and slightly after WW 2, and knowing a lot of people there, we used to hear quite a lot about on-going Air Force projects there. I'm thinking of taking a short trip over to Ohio to visit the AF Museum in the next few months, so I will be checking out the history of the XB-70.

If I'm not mistaken, (again, this is from memory), I think Joe Walker was also one of the pilots who was involved in the testing of the X-15; ( they certainly didn't pick any "bozo's" to fly that thing ! )

Based on what you have told us about that crash, apparently ejection seat technology back then was no where near what it is today. I know the Air Force tried a lot of seemingly "hair-brained" schemes back in the 50's, the vast majority of which ended up in complete failure. You mentioned the B-58 Hustler.............we saw a LOT of those back in the early days of that program.

Thanks again for your post, rwessel !

Charley
Stupidity: Doing the same thing over and over again and expecting a different result; Albert Einstein
 
OldAeroGuy
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Feb 12, 2012 7:30 pm

Quoting geezer (Reply 20):
....................when the USAF was testing the XB-70 Valkyrie they always used at least one chase plane as an "observer"; on one fateful flight, the late Joe Walker was flying the F-104 Starfighter chase plane;

It wasn't a test flight. There were other airplanes in the formation including an F-4, F-5, and T-38. All the airplanes were powered by GE engines and the flight was photo op for a GE advertisement.

Here's a You Tube video on the flight:

http://www.youtube.com/watch?v=fCORwUxlNQo
Airplane design is easy, the difficulty is getting them to fly - Barnes Wallis
 
Geezer
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Feb 12, 2012 8:33 pm

Quoting OldAeroGuy (Reply 23):
It wasn't a test flight. There were other airplanes in the formation including an F-4, F-5, and T-38. All the airplanes were powered by GE engines and the flight was photo op for a GE advertisement.

wow ! Talk about timing ! You're absolutely correct OldAeroGuy..........I just this minute logged back on after spending the last hour and a half reading about the whole thing on WIKI ! ( Here's a link that explains the whole thing )
( Very good article BTW; I highly recommend it. )

The USAF summary report of the accident investigation stated that, given the position of the F-104 relative to the XB-70, the F-104 pilot would not have been able to see the XB-70's wing, except by uncomfortably looking back over his left shoulder. The report said that Walker, piloting the F-104, likely maintained his position by looking at the fuselage of the XB-70, forward of his position. The F-104 was estimated to be 70 ft (21 m) to the side of, and 10 ft (3 m) below, the fuselage of the XB-70. The report concluded that from that position, without appropriate sight cues, Walker was unable to properly perceive his motion relative to the Valkyrie, leading to his aircraft drifting into contact with the XB-70's wing. The accident investigation also pointed to the wake vortex off the XB-70's right wingtip as the reason for the F-104's sudden roll over and into the bomber.
[edit]

Well, after reading that, it looks as if Joe Walker's flying was a little "risky" after all. And to lose 2 lives and a 700 million dollar airplane, all over a "photo op"; How sad is that ?

So, the combination of being too close, unable to see the XB-70's wing, and the wake vortex from the wing, all ended up causing the tragedy. The lengthy article also mentions that the USAF also threw 3 officers "under the bus".......just HAD to have someone to blame it on.......

Charley
Stupidity: Doing the same thing over and over again and expecting a different result; Albert Einstein
 
rwessel
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RE: Myth Busters: Flying V Formation Saves Fuel

Sun Feb 12, 2012 11:23 pm

Quoting geezer (Reply 22):
Based on what you have told us about that crash, apparently ejection seat technology back then was no where near what it is today. I know the Air Force tried a lot of seemingly "hair-brained" schemes back in the 50's, the vast majority of which ended up in complete failure. You mentioned the B-58 Hustler.............we saw a LOT of those back in the early days of that program.

Well, there certainly were more issues in the early days, but the podded ejection systems, like the one on the XB-70, have more troubled history than conventional ejection seats.

Basically on the XB-70, the ejection system would pull the pilot's seat back into a pod, close a big clam-shell door over the pod, and then eject the whole pod. The point being to deal with the severe aerodynamic stresses of a high-mach ejection. In White's case, it appears the ejection sequence took an excessive amount of time, presumably due to the G-loads, the retraction system was at it's limit, and then the door closed on White's arm, badly crushing his elbow, and then on landing the airbag did not deploy, nearly killing White in the impact. It does not appear that Cross's seat managed the reatract cycle at all, which given the high (and increasing) G loads, and the fact that to copilot's seat was sequenced *after* the pilot's seat, may have pushed the mechanism past its limits. There is also speculation that Cross had passed out from the G loads (White reported seeing Crosses head "bobbing", as if he were unconscious).

But large ejection pods have a spotted history. One of the B-1As was lost, and a failure of the ejection pod (in that case most of the crew compartment), killed one of the crew. IIRC the F-111, with a similar system also had some issues. The B-58 had a similar, if slightly simpler, system than the XB-70, and again there were several failures.

Not that a conventional ejection is particularly safe, but the bigger pods and capsules are inherently much more complex.
 
ferpe
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RE: Myth Busters: Flying V Formation Saves Fuel

Mon Feb 13, 2012 8:24 pm

Quoting rwessel (Reply 25):
Not that a conventional ejection is particularly safe, but the bigger pods and capsules are inherently much more complex.

Well for a wartime aircraft capable of Mach 3 there is not much alternatives, normal ejection seats will save the life of a pilot until slightly over Mach 1 but not much more and this assumes you have active retraction and fixation of arms, legs and ultimately also the head+neck. Otherwise the aerodynamic forces will tear these of. Further you need face protection otherwise your face cavities get blown out and so on....

There are very few pilots that have ejected over Mach 1 and survived (I had one as an instructor at Flight academy), this is why aircraft like the XB70, B58, F111 supposed to penetrate at over Mach 1 speed into hostile airspace all had these systems. They complicate things tremendously but are necessary...
Non French in France
 
rwessel
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RE: Myth Busters: Flying V Formation Saves Fuel

Tue Feb 14, 2012 7:08 am

Quoting ferpe (Reply 26):
Well for a wartime aircraft capable of Mach 3 there is not much alternatives, normal ejection seats will save the life of a pilot until slightly over Mach 1 but not much more and this assumes you have active retraction and fixation of arms, legs and ultimately also the head+neck. Otherwise the aerodynamic forces will tear these of. Further you need face protection otherwise your face cavities get blown out and so on....

There are very few pilots that have ejected over Mach 1 and survived (I had one as an instructor at Flight academy), this is why aircraft like the XB70, B58, F111 supposed to penetrate at over Mach 1 speed into hostile airspace all had these systems. They complicate things tremendously but are necessary...

Several A-12/SR-71 and MiG-25/31 high speed ejections had survivors.

But the problem is not Mach, per se, rather dynamic pressure. In most cases these aircraft flew at high Mach numbers (true airspeeds), but at much closer to conventional indicated airspeeds. Some of the Russian seats have a wind deflector that pops up in front of the pilot to improve things further.
 
ferpe
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RE: Myth Busters: Flying V Formation Saves Fuel

Tue Feb 14, 2012 1:17 pm

Quoting rwessel (Reply 27):
But the problem is not Mach, per se, rather dynamic pressure. In most cases these aircraft flew at high Mach numbers (true airspeeds), but at much closer to conventional indicated airspeeds. Some of the Russian seats have a wind deflector that pops up in front of the pilot to improve things further.

yes, you are right, it is the dynamic pressure which is the problem, I assumed we were at the deck as the tactic for the B58, F111, B1 no longer could be to fly high (and this was a major reason the XB70 was stopped). You can employ wind deflectors, then you have to make sure these create reasonable decelerations as now the pilot takes the deceleration g through the harness as the dynamic pressure does not work on him during the deceleration. This is an additional complication with any enclosed life saving system. There is a good reasons astronauts reentry with the spine first ...
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DocLightning
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RE: Myth Busters: Flying V Formation Saves Fuel

Wed Feb 15, 2012 5:43 am

Quoting tdscanuck (Reply 2):

The C-17 has been working on the formation flying technology required for many years. It's not really a technical hurdle, more of a certification/ATC issue.

One thing I don't understand and maybe you can educate me: With the C-17, a military plane, the military can schedule all the flights to depart one after the other in rapid succession so that it's easy to form up in flight. With a long-range track formation, the airliners all have to leave at exactly their pre-determined times or miss their slot in the formation. This would require not only a high degree of coordination between airlines, but also a lot of luck, because any aircraft with a weather or ATC delay would miss its slot.

What is the plan to get around this?
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RE: Myth Busters: Flying V Formation Saves Fuel

Wed Feb 15, 2012 6:11 am

well said, Doc. Any benefit gained from flying in formation would be lost as they'd have to wait in a marshalling area for the group to assemble over a period of possibly hours (which would of course also dramatically increase the duration of the flights, increasing fatigue life and upsetting passengers).

Military aircraft don't do it for the fuel savings, they do it because there's safety in numbers and it's often necessary for them to work as a team when attacking a single target or provide protection for transports.
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RE: Myth Busters: Flying V Formation Saves Fuel

Wed Feb 15, 2012 7:02 am

Quoting DocLightning (Reply 29):
With a long-range track formation, the airliners all have to leave at exactly their pre-determined times or miss their slot in the formation.

"Exactly" is a relative term here. Airborne rendezvous isn't particularly difficult when it's planned. You've probably got a 5-10 minute "launch window" where you can get everyone together without track deviations and just modifying speed.

Quoting DocLightning (Reply 29):
This would require not only a high degree of coordination between airlines, but also a lot of luck, because any aircraft with a weather or ATC delay would miss its slot.

The entire concept makes no sense without a NextGEN-style advanced ATC system that supports direct navigation, continuous climb/descent, etc. Sequenced arrivals is already an existing product, this is just the reciprocal (sequenced departures). It's not a trivial problem by any means but it's certainly a surmountable problem...by the time we get the formation flight aspects figured out and certified, the ATC side won't look nearly so bad.

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RE: Myth Busters: Flying V Formation Saves Fuel

Wed Feb 15, 2012 12:22 pm

If close formation flying ever would become feasible, I would re-think this proposal:
Aerial Refueling For Civilian Airplanes (by Rheinwaldner May 9 2008 in Tech Ops)

I assume the savings to be even larger than by this pure formation flying.

Imagine a perfect 2000nm range aircraft with the size of e.g. the 77W:

- And then the idea would be to "drag" this ultra-efficient, short range VLA by inflight refueling to any desired location on the earth..

- Wingspan and wingarea of such an aircraft could be reduced heavily.

- Take off thrust could be reduced heavily.

- It would weight much less. That aircraft could have only half of the MTOW (considering that at MTOW almost half of the weight of a 77W can be fuel). Because of highly reduced fuel weight, the whole airframe, gears, engines would weight much less. Even the 777-300 (not ER) is not the type of aircraft we have to imagine. It would have to be an even more stripped down version of the 777. Something like a 777-300 with 767 wings, gears and engines (just to give an impression about what I am talking). A quick cross check of the MTOW of the 767 shows, that the lift and thrust generated by the 767 airframe should be sufficient to carry 350 pax over 2000nm. Such an aircraft could blow CASM of anything else. I mean not just by a bit. About 30-40% beyond anything else.

- The additional effort to maintain tankers should be outweigthed by the savings. In the grand scheme of things they could probably almost be neglected. Old and depreciated machines could be converted to form a dirt cheap tanker fleet that is always operated in proximity to the tanker base. The tankers are not required to have long legs, or offer long station time, much range or speed. They just have to to be good by lifting heavy stuff to cruise altitude.

- Multinational tanker companies could offer huge economies of scale and offer maximized usage of the tanker assets. Airlines would purchase their services like they do purchase e.g. printing services for advertizements.

- Maybe the infrastructure could even be maintained by half state-run organizations that also share a military mandate to refuel aircraft beside their civil aircraft refueling. Because the time when the military has a peak demand for aerial refueling services (wartime) almost always matches the time when civil demand would tend to be very moderate. From the military viewpoint the high cost to operate a large tanker fleet could be partially distributed to civil "clients" (win-win).

- The whole fuel supply chain would be simplified and streamlined. From storage to usage fuel would never have to be transported over long distances (today huge amount of fuel are first transported to and stored into the area of large airports, filled into this MTOW monsters we call long range aircraft and then carried half way round the globe, and this per flight).

- Consider the fuel that is used for the second 3000nm as wasted payload for the first 3000nm of a 6000nm flight, to see what I mean. Today each long haul aircraft, almost more than anything else, is doing nothing else as she does:
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ferpe
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RE: Myth Busters: Flying V Formation Saves Fuel

Wed Feb 15, 2012 7:29 pm

Quoting rheinwaldner (Reply 32):
- Consider the fuel that is used for the second 3000nm as wasted payload for the first 3000nm of a 6000nm flight, to see what I mean. Today each long haul aircraft, almost more than anything else, is doing nothing else as she does:

You are dead right, a modern ULH frame packs the following on it's spec flights:

- 50% empty aircraft

- 40% fuel

- 10% payload  Wow!

It is a bit scary really   
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RE: Myth Busters: Flying V Formation Saves Fuel

Wed Feb 15, 2012 9:29 pm

Quoting Starlionblue (Reply 4):
And yes, there are often basic physics being tested, such as the infamous airplane on a conveyor belt.

I wonder how that turned out....   
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RE: Myth Busters: Flying V Formation Saves Fuel

Wed Feb 15, 2012 11:35 pm

Quoting tdscanuck (Reply 31):
"Exactly" is a relative term here. Airborne rendezvous isn't particularly difficult when it's planned. You've probably got a 5-10 minute "launch window" where you can get everyone together without track deviations and just modifying speed.

Still, 5-10 minute launch window is pretty narrow. Having three aircraft on short finals when the flight in question is lining up on the runway can ruin that.
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