Aircraft Control and Barber Pole
 

Hi All,

I'm doing a little survey.

I was hoping some here could give their honest opinions regarding Vmo/barber pole and the effects of aircraft control. I would rather start a regular poll that most forums have where you just click on a selection, but it doesn't seem I can here at pprune. Without further ado...

Think of the aircraft you operate.

Now think of exceeding Vmo/Barber Pole at any altitude on your ASI.

Now please think, in your expert opinion, when you feel your aircraft will no longer be controllable/survivable above such limits.

If you would be so kind, please copy/paste the following in your reply which applies to you and the aircraft you fly. When replying with your selection, please post the aircraft which you operate.

10-30 knots over Vmo/Barber Pole
30-50 knots over Vmo/Barber Pole
50-70 knots over Vmo/Barber Pole
70-100 knors over Vmo/Barber Pole
100-130 knots over Vmo Barber Pole
130-150 knots "
150-200 knots "
200+ knots "

Thank you in advance for your participation.

Ok, I'm no pilot. Just occasional self loading freight. All the same, I have to ask. Why do you think anyone's opinion about what the effects of exceeding Vmo are is of interest? Given that it is a limitation derived (hopefully) from an understanding of the airframe limitations, taking into account a safety factor, what useful knowledge could be gained by asking what pilots who presumably don't intentionally exceed the limit think will be the results if they do? If 95% of them were (hypothetically) to say that they would be happy to exceed it by 50 knots, would this justify revising Vmo?

I'd like to think that v-speeds are based on analysis, not on straw polls.

I have no first had experience whilst exceeding Vmo, however...I know some of the Lockheed test pilots that did, and they report no particular problems exceeding Vmo by 30 knots and Mmo...to M.98 (Mmo M.90)
Type, Lockheed L1011.

Rather a strange question.




However, one of the 767's that hit the WTC was indicating 460 KIAS




This is 110 knots over VMO.





Of course they were not planning on using the Aircraft again.

Though this may be relevant, I think one needs to be a little wary of the 'I know somebody that got away with it' argument. This is a little prone to what statisticians refer to as 'sampling bias': you aren't likely to have a conversation with somebody who tried it, and killed themself in the process...

V-speeds are based on analysis. Specifically flight and wind tunnel tests.

With that said, it is always nice to know what actual pilots think their aircraft can perform.

Opinion based on experience counts for something. No?

In other words,

Would you take a corner in a Hyundai at the same max speed you would a Corvette?

How would you know the difference if you never lost control in either?

Wrong.
I know many of the guys personally....and they certainly did not get 'killed' in the process.

Really?

Which one?

Very strange question, however an answer from 15 years ago.

My initial DH8 (300) endorsement was conducted in the aircraft and fortunately for me, the Training Capt was a Bombardier test pilot.

In conversation one day he mentioned that during the type certification, the aircraft was in a dive at Vmo +, from memory somthing like 270 kias, with a Vmo of 242 (if memory serves), when the gear extended for no apparent reason.

Post flight inspection revealed no damage to gear, gear doors, or airframe despite the airframe being some 30 kts over Vmo, and the gear extending with a greater over-speed.

Thanks for your reply 411A.

At what speed do you think they would have reported problems?

Vmo+50? +70? +100?

Do you have a source for the test pilot flight?

Thank you for your reply Capt Claret.

So it appears your aircraft underwent un-commanded control at 30 knots over Vmo.

Thanks again for your reply.

Now that has to be a classic example of a half-quote. I've no reason to doubt that you know people who have exceeded Vmo, and got away with it. How do you think they would have told you about it if they had exceeded Vmo and killed themselves? What part of 'sampling bias' is it you don't understand?

I don't know much about aircraft certification and airframe limits, though I do recall that new airframes are often tested in steep dives in excess of Vmo, to determine the maximum dive speed Vd? If you could find the figures for Vmo and Vd for a given aircraft that would go a ways to answer your question, as obviously the test pilots did not experience any loss of control up to this speed.

Thank you for your reply mig3.

Yes, I understand.

It is the classic V-G flight envelope.

http://upload.wikimedia.org/wikipedi...ceEnvelope.gif

But what I'm asking here, is the opinions from experts based on experience.

So far we have un-commanded changes to the fundamentals of flight based on Capt Claret, at 30 knots over Vmo.

411A claims L1011 crews experienced no changes at 30 knots over Vmo.

All I am doing here is to find out expert opinion of those who have time in their aircraft and when they THINK (based on their experience in their aircraft), they would lose control over Vmo.

I am in no way asking anyone to try it, or admit they have. Just opinion only.

"got away with it"...rubbish.
It was part of the flight test program.

Clearly you know nothing about flight test procedures.
Therefore, you will be ignored by those that do.
No surprise.:ugh:

I'd hope an expert could tell the difference between what they THINK would happen, and what they KNOW, and not give credibility to speculation.

Are you actually capable of comprehending a simple statement? I merely pointed out that knowing people who had done something isn't necessarily proof that it is always safe. Can you please explain the flaw in my reasoning?

- any questions?

RTM - I don't think I have even entered the '10-30' bracket!

Opinion based on experience is very different than speculation.

Do you disagree?

Hi Ralph t.m.

Mad Flt Scientist posted a very comprehensive answer in Dec 2006
here.

Based on his answers - I reckon my A320 would still be controllable at MMO + .07 Mach or VMO + 50 kts. However, I have no intention of deliberately verifying this.

P.S. Before everybody with a copy of A320 FCOM explains how the protection Laws operate - let's assume they were turned off / failed for some reason. (e.g. Frozen pitots)