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Re: The Square-Cube law........

By: faul in ALEA | Recommend this post (0)
Wed, 25 Jun 14 12:11 AM | 53 view(s)
Boardmark this board | The Trust Matrix 		Msg. 15739 of 54959
(This msg. is a reply to 15738 by Cactus Flower)
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Two Points........

1."Beyond MD (= MMO+0.07) / VD (= VMO + 31kts) (A320 family), structural disintegration can occur."

31kts x 1.15=36mph above rated VMO........

Your simulation claims 700 mph on a plane rated
as 350kts VMO at Sea Level......

350kts x 1.15=402.5MPH

If structural disintintegration can occur 36MPH
over VMO what do you think would happen at
297.5MPH above VMO?

2."Typically, to achieve this speed, the aircraft must enter a dive (steep descent), as the engines cannot produce sufficient thrust to overcome aerodynamic drag in level flight"

So how could the Engines produce enough thrust
for the Aircraft to fly 297.5MPH over VMO at
sea level,level flight?

Your simulation is a complete fabrication.......!!


"The dive speed is the absolute maximum speed above which the aircraft must not fly. At the dive speed, excessive aircraft vibrations develop which put the aircraft structural integrity at stake.

On the Airbus fly by wire aircraft, it is not possible to reach the dive speed, due to the flight envelope protections available in normal law. If the sidestick is maintained full forward, and the airspeed crosses VMO/MMO, the pitch nose-down authority smoothly reduces to zero at approximately VMO +16 / MMO + 0.04. This however, does not guarantee the airspeed stabilizing at this speed.

If MMO + 0.04 / VMO + 20kts is reached or exceeded, then a structural inspection is necessary. Beyond MD (= MMO+0.07) / VD (= VMO + 31kts) (A320 family), structural disintegration can occur."

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The above is a reply to the following message:
Re: The Square-Cube law........
By: Cactus Flower in ALEA
Tue, 24 Jun 14 7:15 PM 		Msg. 15738 of 54959

okay. so i am glad you finally acknowledge the key point. the break up limit doesn't seem to be available.

so what is the numbers basis for a theory that the plane would have broken up when flying into the wtc?

i see a lot of unknowns rather than certainties.

1. the air speed of the aircraft as it flew over manhattan isn't known. radar readings point to a ground speed of 510 knots. video images suggest a ground speed that was lower. average west>east wind speeds suggest air speeds are 5% less than ground speeds on average but we don't know wind speeds for that day. so the air speed of the plane is not known.

2. we don't have access to an authoritative source for the break up speed of the aircraft. you have put forward velocity maxima which i contend are operating velocities. operating velocities are speed limits to reduce wear and tear and therefore to avoid higher maintenance costs. an aircraft engineer, whose evidence you doubt, contends that break up speed is constant in relation to the speed of sound. the speed of sound itself varies by altitude. the shock waves the atmosphere produces relate to the speed of sound at any particular altitude: they vary by air density and heat but appear to be constant at a particular mach number regardless of altitude. i believe these shock waves represent atmospheric resistance. this is how i read wikipedia's discussion of mach numbers but i am no expert. at any rate, neither of us has found an authoritative break up speed for this plane, and so we are left in limbo.

3. even if atmospheric resistance is constant relative to mach numbers, which i think you dispute, i believe friction and atmospheric heat in the engines may plausibly lower the speed limit of planes at low altitudes. i don't know by how much.

4. to reach higher velocities also requires thrust. the engine thrust capabilities required to reach specific velocities at specific altitudes requires a calculation. that calculation is something neither of us is offering. indeed i think neither of us has the knowledge base to perform it. the same aircraft engineer informs us that the boeing simulation software indicates the 767's engines can reach the thrust levels required to achieve the impact velocity. you doubt his integrity.

so basically, a theory that requires certainty in the figures and a decent knowledge of airplane mathematics is something that we do not have. what we have is a derivative conspiracy theory, on the one hand, and a porridge of doubt on the other.

not sure why you want to continue.


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