Why not to go past VNE

[ToiletDuck]

Why should flight speeds above VNE be avoided?
A)Design limit load factors may be exceeded, if gusts are encountered. B)Control effectiveness is so impaired that the aircraft becomes uncontrollable. C)Excessive induced drag will result in structural failure.

The book says A. That sparks my question of what are aircraft really capable of speed wise? Is it perfectly safe to do this IF it's clear blue skies and perfectly calm?

 

[siucavflight]

That sparks my question of what are aircraft really capable of speed wise? Is it perfectly safe to do this IF it's clear blue skies and perfectly calm?

No it is not wise, and no you should not go past it. That is why it is called a NEVER EXCEDE speed , they already have a speed for flight above a certain airpseed in nice weather this and it is Vno. I suppose you are looking for a Voibs speed (only excede in blue skies.)

 

[ToiletDuck]

That's why i was wondering why the answer would not simply be C. The higher seed would cause high drag on the aircraft that could exceed it's limitations no? Isn't that what is basically is ripping it apart?

 

[Steveair]

Vne is a published limitation for the aircraft. I would never go by it myself, but it can be done... in theory. The FAA (don't ask me where to find this), requires aircraft to withstand stresses at levels 25% greater than Vne in order to keep people who try stupid things alive.

 

[ToiletDuck]

My teacher always puts it "They do it to keep you from hurting people on the ground... They don't care about you"

 

[uwochris]

For C, it says "induced drag," so I think they are trying to trick you. Remember, induced drag is low at high speeds, even though total drag may be high (predominantly parasite drag).

Vne is based on excessive pressure forces caused by the high drag. Once you exceed this speed or get close to it, structural failure can occur.

 

[vclean]

In addition to the increased drag beyond Vne, control surface flutter can become stong enough to cause catastrophic failure. As an aircraft ages, control surface linkage wears and introduces more play (looseness). This can reduce the safe speed margin designed in the airframe as flutter can become significant at Vne.

 

[CptOver]

I think of Vne as more of an antiquated way of giving a pilot a hard airspeed to avoid exceeding with a slight oops factor added in. In level flight and smooth air you could exceed Vne (to a point) with no problems. (it will not rip the wings off) They modernized this in larger aircraft by giving them a variable Vmo (max operating speed) or "barber poll" to correct IAS for altitude to accurately reflect true IAS. But these systems were expensive and only relevant to aircraft that could exced these speeds in level flight at higher altitudes. (ie C-172 can only exceed Vne in steep descent)

Vne does add an oops factor for this end all number, for this discussion lets call wings ripping off Vdead....

The aircraft and attitude that it is being flown effects Vdead greatly...
1. The speed and angle at which you change pitch or roll (including changes due to turbulance) increases load factor thus increasing Vdead
2. The size, shape and lack of flying tail could lead to Mach tuck and thus Vdead
3. Configuration of the aircraft (flaps/gear) increase Vdead
4. Altitude affects Vdead because of airspeed inaccuracy at higher altitudes. Higher Alt = Lower IAS = Lower Vdead
5. Original and published Vne based on new aircraft straight from factory with new metal/bolts torque to published settings

Newer "glass cockpit" aircraft actually calculate a moving Vne (Vmo/Vmmo) as well as a minimum manuvering speed based off of pitch/roll/configuration at all altitudes.

So overall answer is you can exceed Vne, but if you do you are bascially "test flying" it and not guaranteed that your used aircraft maintained by your mechanic will hold together in a 60 degree bank turn at Vne. Understand what the speed is and respect it.

I would answer A.

 

[Flyin Tony]

**CENSORED****CENSORED****CENSORED****CENSORED** starts flying off the plane. They did test on the twin comanche and it got rudder flutter very very bad.

 

[Kawasumi_Kichou]

Good discussion of Vne vis-a-vis Vc and Vd here:

http://www.avweb.com/news/airman/184284-1.html

Scroll down to the "Speed Kills" part.