Is VMO an absolute aerodynamic limit ?

[Kiwiguy]

Why don't jets have VNE ?

Previously under CARs all jets had published VMO and VNE figures for example:

Type: VMO / VNE (kts)

B747-200: 375 / 445

DC-8-73: 352 / 406

DC-9-30: 350 / 425

DC-10-30: 356 / 400

The B757-200 however has a VMO below 10,000 ft of just 250 knots because the windshield isn't certified to withstand birdstrike above 313 knots. Above 10,000 ft the 757 is VMO limited to 350 knots.

The son of Bill Lear, John lear and I are debating the point in relation to his 9/11 conspiracy theories. 9/11 conspiracists maintain that novice pilots could not have flown a 757 into the Pentagon because it was VMO limited and thus the dive at 350 knots was not achievable as it exceeded VMO.

I say this is balderdash. The VMO limit is a windscreen issue only. John Lear maintains that VMO is an absolute aerodynamic limit on the airframe above which flutter would prevent novice pilots performing the manouveres.

I say it is not an absolute speed limit. I say there is a higher limit VNE at which, then loss of control is possible. Trouble is FAR Part 25 no longer requires demonstration of VNE.

John Lear and I have also crossed swords over United 175 which flew into WTC2 at 466 knots (according to radar tape analysis). John Lear maintains a novice pilot could not have done this.

In fact I am not quite sure what John Lear is saying because in some instances he seems to suggest that the 767 could not have flown at that speed at all because it exceeds the 767 VMO (which Lear says is impossible).

At other times he simply says the hijackers lacked the skill to do so. (case of conveniently shifting the goalposts).

Comments ?

[411A]

Having had a very few 'discussions' with JL before, his points of view nearly always were at odds with others...although he most certainly did not want to discuss with yours truly the technicalities of the Lockheed L1011 (and especially the FMS installed therein) as clearly he was at a severe disadvantage, figuring that perhaps I had forgotten more that he would ever know about the subject...which I suspect was a true conclusion.

I cannot address the merits of the B757/767 as I have not flown these, however the L1011 was flown well in excess of Vmo during flight test, and indeed, considering Mmo, which for the TriStar is M.90, flight test was performed, according to Lockheed test pilots that I know...at M.98.

So, excess speed certainly is possible, but only a fool would go there....unless you were a properly trained test pilot.

Of course, exceeding Vmo/Mmo will sound the overspeed clacker, but simply tripping the appropriate circuit breaker would 'fix' this inconvenience.

[Mad (Flt) Scientist]

John Lear maintains that VMO is an absolute aerodynamic limit on the airframe above which flutter would prevent novice pilots performing the manouveres.
Thus proving quite conclusively that engineering skill is not an inherited trait, because that statement is complete and utter garbage.

VMO (and MMO) are exceeded in flight test on every single aircraft. Even VDF/MDF (or VNE) are not ABSOLUTE limits - they are the limits beyond which it is no longer known to be safe - not the limits where it is known to be dangerous. Margins between VMO and VDF are typically of the order of 50-75 kts (just like the old VMO/VNE splits); margins between MMO and MDF are typically of the order of 0.05M-0.07M.

In fact, its a requirement that VDF/MDF be DEMONSTRATED in basic certification.

[flyboyike]

Speaking of John Lear, here's a trivia question:

True or False. He has a sister named Crystal Shanda Lear, as in crystal chandellier.

Well, it's false, her name is just Shanda Lear. No kidding.

[Kiwiguy]

Some choice quotes from a conversation recently with John at Abovetopsecret's website:

It [VMO] is an aerodynamic limit which will activate the overspeed warning horn which is very loud and very annoying and its made that way so that there is no misunderstanding about what it means. It means 'you are going too fast." To suppose that an inexperienced hijacker was flying a profile with incredible skill at 787 feet per second with the overspeed warning horm blowing is to ignore reality. It could not happen and it did not happen.

No they don't. That statement is complete false. VNE applies to propeller powered airplanes or those certifcated under the old CAR 4b. VMO is velocity max operating, MMO is mach maximimum operating. And those limitations are all that are given to the pilot, printed on the airspeed indicator and published in the limitations manual. VD and MD are certification limits and are much higher but not to be used or even known about by other than certification test pilots.


The VMO is a speed limit for descent from altitude such as towards an airport and is normally intended to avoid structurally harmful wing bending. This is not the VMO limiting factor for the 757/767. It is not the maximum speed at which the aircraft may be flown.


This statement is incorrect and absolute poppycock. It is most definately the maximum speed at which the aircraft may be flown.

[skiingman]

I'm no freaking aero pro, but even I can tell you that "wing bending" is not likely to be the boundary condition that VMO is predicated on.

[Kiwiguy]

So back to the topic, is the above just semantics ?

I mean is it just that instead of VNE I should call it MNE ?

and likewise VMO is MMO ?

Can anybody tell me if the 757 or 767 have VNE or MNE numbers published anywhere ?:sad:

[Mad (Flt) Scientist]

1. There's no such thing as "MNE" - the "never exceed" and "normal operating" concepts behind VNE and VNO apply only to aircraft where Mach effects are not explicitly listed in defining speeds (even though good engineering should account for Mach beffects, the resulting limitations strictly shouldn't be expressed as Mach number limits)

2. VMO is not MMO. Rather VMO and MMO are just ways of saying "the maximum operating limit where airspeed effects dominate" andn "the maximum operating limit where Mach effects dominate" - taken together they JOINTLY define the maximum operating speed limit.

3. 757 and 767, being Part 25 aircraft, do not have VNE defined; VNE is a Part 23 concept. Even if you somehow tried to certify a 757 as a Part 23 aircraft (!) 23.1505(c) would mean that it STILL had a VMO/MMO and VD/MD, not a VNE.

However....

Part 23, per 23.1505, uses both VNE and VMO/MMO nomenclature - depending on whether the aircraft are "turbine airplanes or to airplanes for which a design diving speed V D /M Dis established under §23.335(b)(4)" or not. Therefore, one can attempt to crudely relate the terms.

Assuming that you have defined the structural design speeds VC and VD for your aircraft.

If you now follow 23.1505(a) and (b) you get:

VNE=max(0.9VD or 0.9 max speed demonstrated per 23.251)
and
VNO=max(0.89VNE or VC)

If you follow 23.1505(c) instead you get:
VMO =max (VC, safe margin to VD)
where the safe margin is determined by various speed/gust upset/recovery tests.

In practice, what usually happens is that both VNO and VMO end up being equal to VC. So that would imply that
VNE=1.1(VNO,VMO)
and
VD=1.1VNE

So if your VMO/VNE were 300kts, say, that would imply a VNE of the order of 330-340kts and a VD of about 370-380kts. Basically, VNE ends up being about half way between VMO and VD. Part 25 has such a speed for certification - it's called VFC, and is the maximum speed for demonstration of "flight characteristics". But this is all based on somewhat abusing the certification speed definitions (many of the relations are not "equals" but "not more than" or "not less than" so there's no real way to reverse engineer the speeds for a real case.

Note also that even for aircraft where VNE is the certified speed used, the rules state:
§ 23.1505 Airspeed limitations.
(a) The never-exceed speed VNE must be established so that it is—

(1) Not less than 0.9 times the minimum value of V Dallowed under §23.335; and

(2) Not more than the lesser of—

(i) 0.9 V Destablished under §23.335; or

(ii) 0.9 times the maximum speed shown under §23.251.

23.251 is a FLIGHT TEST DEMONSTRATION. Therefore any aircraft with a posted VNE MUST have been flown at least 10% faster during flight test. Doesn't sound like VNE is a speed where the aircraft is going to be falling out of the sky, does it?

[Mad (Flt) Scientist]

AFAIK, the only Part 25 turbojet aircraft that has such limitation

Any Part 25 aircraft with a Vmo "cut back" below 8000ft/10000ft almost certainly has a similar design constraint. There's nothing else in the design requirements which would drive an abrupt altitude/speed change. (The regs assume a maximum altitude for birds). I can think of a fair few aircraft with such a cutback.

[Kiwiguy]

We have turbocharged condors here, probably fitted with O2 masks on their beaks, flying above 20,000 feet...

Next you'll be telling me they're IFR rated ?

No actually I read somewhere that the 757's windshield is rated to only 313 knots for birdstrike. That didn't come from John.

As mad scientist notes many aircraft are VMO limited by windscreens.

VD, I understand is the dive speed, but in the case of the 757 this is often quoted as the same as VMO. :bored::confused:

I understood that in propellor aircraft VNE was set at 0.9 of VD. Why in a 757 would they be cited as the same ?

Is there an online source to check out V numbers for 757 and 767.

In particular can anyone comment on JL's assertions about wing flutter precluding the B767 attack on WCT2 at 466 knots ?

Anybody care to comment on the alleged "impossibility" of novice pilots diving a 757 at the Pentagon.

I am quite fed up hearing pimple faced kids citing JL as an authority that it couldn't have happened. :ugh:

I would like to invite the knowledgeable folks here to put these rubbish theories to bed once and for all.

[nano404]

Were the terrorists flying all the time ? Is it that hard to hit a building?

John Lear maintains that VMO is an absolute aerodynamic limit on the airframe above which flutter would prevent novice pilots performing the manouveres.

Want to point out that the plane was flying low, 100 ft. and less at 530MPH, cruise speed for the 752, no excessive anything but stupidity. It seems like it dived and levelled some then crashed.

[411A]

Interesting about the 313 knots as a windshield issue.

The L1011's that were on the UK civil register had this limitation, below 8000 feet, as I recall....however it was not an FAA requirement.
Of course, the Brits required other changes as well...scarfed pitot tubes, lower Mmo (M.88) among others, and most distressing of all, you could not select CWS with an autopilot on the ground for takeoff, quite unlike the FAA certified aeroplanes.

Also, further to Vmo and Vne, under present FAA certification rules, if a piston powered aeroplane was re-engined with turbopropellor engines, the previous Vne would go away, and the old piston Vno would then become Vmo on the 'new' turbine aeroplane.

[Re-Heat]

I always thought that many speed limits were the limits at which significant damage to the structure could start to occur - clearly structural failure rarely happens immediately at any operational speed, and flying up to published limits would not break the aircraft at that point in time, but result in many structural repairs to prevent eventual failure at a later date under normal operating conditions??

nano404 - 530mph at 100' will result in an excessive indicated airspeed, well above the limit: the cruise speed is, of course, at altitude where the air is far thinner and less stressful on the airframe.

[nano404]

nano404 - 530mph at 100' will result in an excessive indicated airspeed, well above the limit: the cruise speed is, of course, at altitude where the air is far thinner and less stressful on the airframe.

Meh you think if everything don't ya? Thanks for the pointing that out. Though I guess broken in 3 or all together damage will still occur if a plane hits a building.

[Mad (Flt) Scientist]

Is there an online source to check out V numbers for 757 and 767.

The main design speeds can be found on the Type Certificate Data Sheet, which is a publicly available document.

Go to http://www.faa.gov/, select the 'Licences and Certificates' tab, then under 'Aircraft' there is "Type Certificate Data Sheets (TCDS)" which links you to here (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/MainFrame?OpenFrameSet)

You can then look up a specific TCDS by make/model etc.

For example, this (http://rgl.faa.gov/Regulatory_and_Guidance_Library%5CrgMakeModel.nsf/0/15302E51A401F11A8625718B00658962/$FILE/A1NM.pdf) is the B767-200 TCDS.

Airspeed Limits: VD = 420 KCAS to 17,854 ft/.91M above 23,000 ft, linear variation between these points.
VFC = 390 KCAS to 17,600 ft/382 KCAS at 23,000 ft/.87M above 26,000 ft, linear variation between these points.
VMO = 360 KCAS/.86M
VLE = 270 KCAS/.82M
VLO = 270 KCAS/.82M

[fireflybob]

Isn't it just the case that jet a/c cruising speeds are much closer to the "maximum" airspeed/mach no whereas piston engine aircraft cruise at speeds well below VNE? I always understood that the concept of VMO/MMO was introduced at accomodate cruise speeds on jet a/c.

[galaxy flyer]

MfS: While engineering talent may not be hereditary, the ability to sling BS most certainly IS, in this case. Having listened to LR pilots over the last 30 years, I would not be surprised that the ability was included in the purchase price.

[xetroV]

The main design speeds can be found on the Type Certificate Data Sheet, which is a publicly available document.
Go to http://www.faa.gov/, select the 'Licences and Certificates' tab, then under 'Aircraft' there is "Type Certificate Data Sheets (TCDS)" which links you to here
You can then look up a specific TCDS by make/model etc.
For example, this is the B767-200 TCDS.
Thanks a lot for the link! Very useful.

I was looking for VD (VDF) / MD (MDF) figures for the B737-300, -400 and -800 and for the B747 myself; however the TCDS documents refer to "the appropriate FAA Approved Airplane Flight Manual", which I can't find online. Would you happen to know an online source for those figures too?

[411A]

I was looking for VD (VDF) / MD (MDF) figures for the B737-300, -400 and -800 and for the B747 myself; however the TCDS documents refer to "the appropriate FAA Approved Airplane Flight Manual", which I can't find online. Would you happen to know an online source for those figures too?

You generally won't find this information in the TCDS, as these speeds are not certificate limits.
Many (most) FAA approved flight manuals don't have this information either, as it does not concern the normal line pilot.

It is only the possible concern of the test pilot, who are far more experienced in this rhelm of operation.
I have known pilots in the past who routinely operate right at the barber pole during descents, the overspeed clacker sounding repeatedly and continuously.

These folks are generally classified as being...not too bright.:ugh::ugh:

[xetroV]

Just to clarify: I do have the FCOMs for these Boeings, and indeed you won't find VD/MD or VDF/MDF figures there. But I think what the FAA is referring to in the certification documents comprises of more than just the FCOM.

[LoadMan]

I always thought that many speed limits were the limits at which significant damage to the structure could start to occur - clearly structural failure rarely happens immediately at any operational speed, and flying up to published limits would not break the aircraft at that point in time, but result in many structural repairs to prevent eventual failure at a later date under normal operating conditions??

That is one limit. Maneuvers may lead to excessive airframe loads above VD/MD, which is the limit where maneuver loads have to be calculated and the maneuver loads above VD are tghus not accounted for. It is generally not recommendable to give maximum rudder at those speeds (while most likely will not lead to structural failure if it is applied with some respect).
Another problem would be gust, which can be quite challenging for the airframe at such air densities.
I would assume that for "good" configuration (lots of weight in the wings) and careful handling the VMO can be exceeded by a fair margin at low altitudes. Weather should be corresponding.

[fleecy]

Mmo is not purely for jets. Modern fast turboprops ( say the Dornier 328 ) will climb to 31,000' where permitted. Its limits from memory are 270 KIAS or Mach 0.56.
The Embraer 135/145 series limits are quoted as:
Mmo/Vmo M0.78 OR 320 knots from 37,000 feet to 10,000 feet, reducing in a straight line to 250 knots between 10,000 feet and 8,000 feet.
Below 8,000 feet it's a windshield limit. (In the U.K. it's normally an airspace limit of 250 knots below 10,000ft. anyway.)
The Manual states: Vmo/Mmo may not be deliberately exceeded in any regime of flight (climb, cruise or descent).
The Embraer will exceed its published limits straight and level. Below about 25,000 feet, 320 KIAS will be reached first. Above that level, it will be M0.78 reached first. Review your tech books for an explanation.
A Company will issue its Pilots with procedures regarding the reporting of overspeeds in consultation with the Manufacturer. It is likely that an overspeed will ground the aircraft until inspected. Information is held by Engineering regarding checks to be made on the aircraft. The aircraft is not likely to sustain any damage with short overspeeds- that's why the limits are set where they are.

[ChristiaanJ]

Some posters seem to be less than clear about the fact that VMO and MMO are certified limits.
The aircraft does not promptly come apart, but you start to compromise the "advertised" life of the airframe, when you exceed those limits.
To establish those limits, the aircraft has been flown to well beyond those limits in a carefully controlled manner. Concorde has an MMO of 2.04, but the certification aircraft went up to M 2.23. For those who know the Concorde story: it was one of the reasons the two cerification aircraft (201 and 202) never went into service in the end. It was extremely difficult to assess how much of the aircraft's "life" (in terms of fatigue cycles) had been used up by the certification flights to the edges of the envelope.

[ChristiaanJ]

If the US/FAA uses low altitude turkeys made in USA, they better come down here in Andes, and revise their certification standards. We have turbocharged condors here, probably fitted with O2 masks on their beaks, flying above 20,000 feet...
Next you'll be telling me they're IFR rated ?
No actually I read somewhere that the 757's windshield is rated to only 313 knots for birdstrike.
As mad scientist notes many aircraft are VMO limited by windscreens.
"We have turbocharged condors here...", well, some of the vultures in India must be on nitrous oxide, then, since there are reports of vulture bird strikes at close to 30,000 ft.

Now bear with me a sec.
VMO is IAS, no?
Now (off the top of my head) 300 KIAS is over 500 KTAS at those altitudes.
And for impacts such as birdstrikes, it's TAS that defines the energy of the impact, not IAS, so the energy is about three times that at sea-level.

Oops.... do we have a problem?
Should we start fitting condors and vultures with TCAS?

[AirRabbit]

A VERY interesting exchange of facts, gentlemen (ladies?)… thanks much to all of you for that.

Of course, while I don’t know for sure the reason behind Kiwiguy’s original question, I would assume it was due to the significant contrast between JL’s reputation together with his absolute statements about the fact that airplanes simply could not have been involved in the 9/11 crashes (i.e., the airplanes wouldn’t have been able to stay in one piece – of course, I think his comments are primarily limited to the AA77 crash at the Pentagon) AND the “official” US government’s claims that this is exactly what happened. JL also is of the opinion that a “novice” pilot, like the one alleged to have been at the controls of AA77, simply could not have flown the airplane the way it would have to have been flown to match the government’s story - reference Kiwiguy’s quotes in his July 6th quotes of JL’s comments.

I’ll not go into the details of the “strange” theories that JL offers to counter the governments claim that AA77 struck the Pentagon. Suffice it to say that I, too, have had an opportunity to exchange “opinions” with JL, and have come away with much the same opinion as BelArgUSA. Up to this exchange I was completely unaware of his claims regarding UFOs, but, and without trying to offer specific criticisms of JL, that knowledge does explain a lot of what may be behind some of his “fringe” 9/11 theories.

[NW1]

ChristiaanJ: We flew Concorde to a Mmo of 2.00, I did know what Mach number the overspeed went off at but, along with an unbelievably huge amount of data painstakingly learnt over 6 months, I have sadly forgotten. RIP the highest achieving airliner ever built.

[ChristiaanJ]

ChristiaanJ: We flew Concorde to a Mmo of 2.00, I did know what Mach number the overspeed went off at but, along with an unbelievably huge amount of data painstakingly learnt over 6 months, I have sadly forgotten.Formal Mmo was 2.04.
As SLF I've been up to M 2.03, in the development sim at Filton I've been up to M 2.11... and no, I can't remember either anymore when the overspeed warning started....
RIP the highest achieving airliner ever built.I'm glad to be able to say I've been part of it.

[NW1]

<<Formal Mmo was 2.04>> Not if you wanted the type rating (ground school taught 2.00) ... :)

But you would see more, and Mach #s in excess of Mmo for two reasons:

1) from the cabin the Marilake display was far from accurate (it had a big delay in it to stop it flaying around and on those hot days when we were struggling in the cruise climb a couple of hours of M1.98 would dissapoint the customers so it would read M2.00 - same for a "subsonic" charter - very common to see M1.00 on the Marilake if the true Mach had temporarily "bracketed" over the normal M0.95 subsonic cruise)

and 2) Concorde was designed to be flown right up to Vmo / Mmo at all times, and so small and regular excursions were common and part of the operation - it was not always easy to persuade the blunties running fleet audits that the overspeed warning was SOP and did not need an ASR, we'd have drowned in paperwork if so.....
Brgds

PS: O'Speed warning went off for:
Tmo +7 degrees C
Vmo +6kts
Mach >=0.95 with visor not locked up
Vc > 270kts with nose below 5 degrees
It didn't have a trigger for Mmo, but based itself on equivalent Vmo, FWIW

[ChristiaanJ]

NW1,
"Max Cruise" was a nifty combination of Vmo = 530kts IAS, Mmo = M2.04 and Tmo = 127°C.
I should know, worked on it.

I know about the "cheating" on the Marilakes..... at some point recently there was a serious discussion about getting a few to work again so I went through the documentation. Unfortunately some of the digital protocols used seem to have been lost forever.
The Marilake never showed anything beyond M2.00.

And "my" Mach 2.03 was on a French Concorde.... no cheating Marilake, just a digital voltmeter calibrated in Mach straight from an ADC pot :)

As to the overspeed warnings, I'd have to dive into the doc, but I expect you're already quoting from doc, not memory, so no need to doubt your info.

[NW1]

Well whatever.

Max Cruise mode on the BA aircraft flew the aircraft to M2.00 / Tmo (it didn't always do too well with the latter, but it did fly to M2.00 pretty well).

[ChristiaanJ]

NW1,
Looks as if we were both right.... the flight envelope limitation is M2.04, but Max Cruise does fly to a limit of M2.00, my mistake.

[NW1]

Well; it hardly matters now really - and that's the shame.

[ChristiaanJ]

Well; it hardly matters now really - and that's the shame.I couldn't agree more.

But at least there are a lot of "flight simmers" (I'm not one, BTW) who still work on getting every last detail right, even now, so at least some of the memory lives on.

[TFE731]

Here is a quote from the Falcon 900EX AFM

“CAUTION
The maximum operating limitspeed VMO/MMO must not be deliberately exceeded in any regime of flight (climb, cruise, decent) unless a higher speed is authorized for flight test or pilot training.”

As VMO may be deliberately exceeded in some circumstances it can't be an absolute limit.

By the way, for those of you who have not had the pleasure, Dassault aircraft fly beautifully.

[Mad (Flt) Scientist]

I believe similar wording exists in almost every flight manual.
Exceedence of Vmo to ensure the overspeed warning is properly active is a routine production flight test activity on many types, too.

[AirmanDave]

Just jumpin in to open up some more discussion...
I imagine mostly all of you are fighting to prove that 9/11 happened the way the govt says it did, so I'm not going to fight with you all. First I'd like to insist that you pull off of the John Lear bashing a little and concentrate on the aspects that bring him to his conclusions. Maybe exceeding VMO won't "bend wings" or cause "flutter." I don't know, never tried it... and if I did I certainly wouldn't admit it (looks around for FAA inspectors hehe), but going off of the structural damage that could be caused by an overspeed condition, maybe we could converse about how Center of Pressure (Lift) moves over the upper camber of the airfoil as speed is changed, especially in a swept-wing aircraft. I may be really tired right now and forgetting something, but I know this is where the term "Mach Tuck" comes into play. Also for you all talking about how jets fly up near MMO at cruise... OF COURSE THEY DO. What is the point of spending all that time and fuel (money) to climb to say FL350 (meaning 35,000 feet). Its definately not for the view! Air is thinner at altitude. As air thins, there is less resistance and the aircraft can penetrate the air with much less energy required, therefore giving you a faster ground speed. This is also why those "v speeds" are so much higher at altitude (minus the fact that there usually are no birds up there either, in the case of the 757). Also we have a problem called "Coffin Corner" at high altitudes... which comes from how the speed of sound (Mach) decreases and stall speed increases with altitude. It's a tiny window of airspeed that the pilot must stay within. Blow it and you're done. The higher you go, the smaller the room for airspeed fluctuation. Slow down too much, you stall the aircraft, speed up too much and you overspeed, which then results in "Mach Tuck." These are some reasons why jets fly near MMO all the time at cruise. Time and Safety. By climbing to high altitudes and flying fast, the jet is saving time and money and providing safety by keeping the aircraft away from a stall at altitude.

What about Parasite Drag at Sea Level vs FL350? At Sea Level, the very dense air going into the Pratt & Whitney 4062 turbofan blades would cause a lot of air to get jammed up like a dam at the engine inlet, in turn causing massive amounts of parasite drag. Throttle setting would also be a factor in this discussion... More throttle, more air being used, (less parasite drag?), less throttle, less air being used, (more parasite drag?). Also, there is such a dense amount of air going into the compressor section that the combustion would be hotter and faster, in return spinning the fans faster and causing detrimenal exceedances on the N1/N2 RPMs and Tempurature limits, which would then blow the blades off the turbines, causing the engine to lose mechanical power and burst into flames.

You can tear this up all you want, since I'm just pulling it out of what I know vs a logic thought process, (basically my ass, lol), but I know that if you put enough force on the blades of a compressor, it will blow apart, as in an instant explosive force "Wet Start" of a turbine engine and engine failure would occur. Of course, this would not be applicable for an engine that is descending and the RPM and force in increasing gradually. IF the force doesn't blow the engine apart... the overtemp would cause an engine fire which would be very visible to a video camera, though the pilots would still have power, which would deteriorate over time and eventually fail completely. I saw no fires on the 9/11 tapes until after the aircraft crashed. Forget "structural damage" due to overspeed... what about all the other things that we can damage by flying an aircraft out of its envelope?

How would our "novice" terrorist pilots be able to fly wide body aircraft beyond the limits on Boeing's test pilots without over stressing the aircraft while maneuvering anyway other than besides fluke? I've heard from 767 pilots that it maneuvers like a beached whale... intentionally maneuvering and positioning that aircraft into a 200 foot wide building at 450+ knots takes practice and skill. Just cause "terrorists" practiced flying 767s into buildings on Microsoft Flight Simulator doesn't give them the skillset required to achieve such an accomplishment in real life.

P.S. You can barrel roll a 747... I did it on flight simulator!

[galaxy flyer]

P.S. You can barrel roll a 747... I did it on flight simulator!

Proves absolutely ZERO! The sims aero data most certainly ends at about 60 degrees of roll and likely somewhere around 30 degrees of pitch.

GF

[ChristiaanJ]

Has anybody understood why this "AirmanDave" keeps waffling about "overspeed" and Mmo, and all that? If my 17-year old son (way back) could fly BOS-JFK IFR on the Atari 800 MS FS (two hours in the Cessna), and land properly at JFK, why couldn't a couple of terrorists, with basic flight training and a reasonable idea of the 767 cockpit functions and handling, aim at the WTC towers from miles away (VMC, IIRC) and hit them? I probably could.

Troll country, IMHO.

galaxy flyer,
The fact that you can barrel roll a 747 on MS FS proves nothing.... not even that it hasn't been done in real life!!
It's been done with enough other "big 'uns" (707, Vulcan, Concorde, for some of the definitely confirmed ones).
Would be interesting how many other ones have been quietly barrel rolled somewhere out of sight of prying eyes.....
Anybody for doing it with an A380 ?

CJ

[stilton]

Airman 'Dave' it is hard to know where to start addressing your incoherent aerodynamic babble.


'V speeds higher with altitude' ? 'flying at MMO to stay out of coffin corner'


'A 767 flying like a beached whale'


I have flown the 767 for 10 years and can state categorically it is one of the most responsive transport jets flying.


As to your other aeronautical 'theories' I suggest a little more research or stay with MS :=

[ampclamp]

Kiwiguy, no vmo is not the absolute structural limit.he's talking nonsense.
There'd be a lot badly compromised aircraft out there otherwise.

I've been vne and a smidge higher in a prop driven craft numerous times on test flights and I'm still here.
Its a tad scary, the buffeting was quite bad.Would not want to go much harder.

[airbond]

I believe the old B727 is the fastest of all the Boeing models.

Correct me if i am wrong, but it has 2 max speed modes which you could change, the fastest 380 Kts indicated!

[Mercenary Pilot]

Would be interesting how many other ones have been quietly barrel rolled somewhere out of sight of prying eyes..... Yeah but, it does take a bit more than average skill to barrel roll an aircraft properly in the real world. The consequences of getting it wrong in a transport cat jet would be..... messy! :E

These are some photos of a biz jet that was rolled by a pilot who's imagination outweighed his flying ability ("Duh, it worked on MSflightsim").

http://img520.imageshack.us/img520/8263/twistedhawker1.jpg

http://img13.imageshack.us/img13/8599/twistedhawker2.jpg

Also worth noting, AirmanDave has resurrected a thread that's nearly 2 years old.

[ChristiaanJ]

Yeah but, it does take a bit more than average skill to barrel roll an aircraft properly in the real world. Couldn't agree more....
But then, "Tex" Johnson, Rory Falk and Jean Franchi were pilots of "a bit more than average skill", you'll have to admit.

BTW, thanks for the photos!

CJ

[DC-ATE]

AirmanDave -
I may be really tired right now and forgetting something, but I know this is where the term "Mach Tuck" comes into play.

MACH TUCK...MACH TUCK ??? Mach Tuck is watt I dive don ta oad.:}

[safetypee]

Re photos: if you are imprudent enough to try something unusual then you need to know the possible consequences resulting from the manoeuvres, and the differences between the types of manoeuvre – in this instance between multiple snap rolls and a barrel roll.
Generally the latter being less stressful and ‘gentle’; whereas the former might involve roll/yaw coupling, but neither necessarily involving VMO.

[Mercenary Pilot]

But then, "Tex" Johnson, Rory Falk and Jean Franchi were pilots of "a bit more than average skill", you'll have to admit.I certainly would. :ok:

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Apparently the cause of the damage to the bizjet was the pilot realising that he had screwed up and tried to pull through the manoeuvre, which is also what most pilots tend to do when learning how to do a barrel roll.

[ChristiaanJ]

As far as we know, the Concorde barrel rolls were never caught on film.

More's the pity, since during the filming of "Airport 79 - Concorde" Jean Franchi proposed doing a real barrel roll in front of the camera instead of that stupid loop they used in the end.

Oh, and ... during the event for the 40th anniversary of the 1st Concorde flight, André Turcat again confirmed the barrel roll stories. What annoyed him most about it, he said, was that he hadn't had the opportunity of doing one himself....

[Mercenary Pilot]

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Any excuse for a Concorde video. :ok:

Sadly no footage of the stunt itself although Brian Walpole (British Airways) discusses "unwinding" her alongside Jean Franchi (Concorde Test Pilot). :)

[ClippedCub]

I liked the descend and landing.

concorde cockpit - Google Videos (http://video.google.com/videosearch?hl=en&ie=UTF-8&q=concorde%20cockpit&sa=N&tab=wv&um=1#)

[ChristiaanJ]

ClippedCub,
Another bit pirated off the original 5-hour 2 DVD set from ITVV...

Well worth having if you're a Concorde fanatic (like undersigned).

[ClippedCub]

Thanks, didn't know about the DVD, will look it up.
Pilot's motto - "No such thing as too much performance."
Customer - "Performance costs money"