Wow.
Definitely not for the faint hearted..
How “close” to Vne did they get? 
From what I can see (not much) they were pointing about 60 degrees down at one point.
I noticed at one point, prior to the pull out, that the guy in the RHS puts his arm over to, I assume, ensure that the guy in the LHS does not pull too hard. It could have been a cautious, involuntary action, but they would at that point have been hurtling to VNE, the cockpit noise also increases at this stage. When testing these types, I am not sure as to how close to VNE they would go. No one actually likes getting close to VNE, do they?
Well, I googled it. 110% of designers theoretical VNE. Debate as to whether anyone actually goes there. If they do, it is TEST PILOT country, with parachutes, and an exit strategy of getting out quickly. These guys did not have parachutes on. Found this
In the spectrum of flight testing we do at the Navy, flutter testing remains some of the riskiest. Before an aircraft even flies we do structural modeling and physical shake tests to determine where the resonance peaks are. When it comes time to do Vne/flutter testing, it is done with a fully instrumented aircraft and in most cases the data is telemetered to the ground so lots of engineers who know what they are doing can take a look at the data real time (not to say we don’t know what we are doing).
For Vne testing, the control surface in question would be instrumented for strain and position and the aircraft will be trimmed to a slower speed than target so if the stick is released it will pitch up and slow down on its own. Then, at incrementally increasing airspeeds, the control surface is “rung”, often by the pilot simply slapping the stick. Engineers will analyze the response of the control surface to determine the damping ratio of the system. As the speeds increases the damping ratio will become smaller. The trending of the damping ratios will be tracked and extrapolated to determine the Vne and the testing will be called off some margin before that speed is reached. This obviously is a simplification, but the process is basicly correct.
Flutter will build energy quickly, so if you go out looking for the actual Vne and it happens to be dictated by flutter and not something else there is a good chance that you won’t be able to recover regardless of piloting ability. Personnally, I would make sure my hinges and control runs were as free of slop as possible, verify the balance points of the control surfaces are as recommended, and test it out to Van’s suggested Vne (because you know someone has gone there at least once).
pierre smith
Holy shit!
They were definitely past Vmo, as you can hear the overspeed warning going off after they pitch down, and they pull the power back to idle and get the speedbrake out.
Looks like a fairly exciting test all round!
BeechBaby wrote:
These guys did not have parachutes on.
If a wing came off in a >Vne pullout, would there be any way for anyone to get out of the cockpit of a narrow DC-9?
BeechBaby wrote:
When testing these types, I am not sure as to how close to VNE they would go.
Aren’t you supposed to fly the aircraft to Vd which is Vne+10%. Or is that only for light aircraft?
A transport aircraft has a Vmo (Max operating) expressed in IAS and an Mmo which isn’t relevant at these altitudes. One can exceed Vmo by a limited amount and only require an inspection after a certain number of cycles (it has happened to me in severe turbulence over the Alps) and the margin is generous.
Vmo is 0.8 Vd in aircraft certified under CS25, and the aircraft is stressed for a 1.5G pull at Vd (and 2.5G at Vmo)
