Piper PA-30 Twin Comanche Aircraft Tail Flutter Test

Video Courtesy NASA

Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, buildings, telegraph wires, stop signs, and bridges. Flutter occurs as a result of interactions between aerodynamics, stiffness, and inertial forces on a structure. In an aircraft, as the speed of the wind increases, there may be a point at which the structural damping is insufficient to damp out the motions which are increasing due to aerodynamic energy being added to the structure. This vibration can cause structural failure and therefore considering flutter characteristics is an essential part of designing an aircraft.

http://www.cs.wright.edu/~jslater/SDTCOutreachWebsite/aerodynamic_flutter_ban...

http://en.wikipedia.org/wiki/Aeroelasticity

This 23 second video clip shows the PA-30 Twin Comanche during a tail flutter test

After being purchased in 1967, NASA 808 was used as a testbed for general aviation flight control research. NASA's first project with the aircraft was the determination of its stability and control characterisitics in the Langley full-scale wind tunnel. The wind tunnel measurements were then correlated with in-flight measurements of the stability and control characteristics at Dryden. This was the first time full-scale wind tunnel measurements of a general aviation aircraft had been made since the late 1930s. As a result of the studies, several changes were made by the contractor to the aircraft to improve its flying qualities. These changes are manifested in later models of the airplane.

Another project involving general aviation was the PA-30 program to define the operating techniques necessary to enable curved landing approaches as a part of routine operation at major airports. The program, in support of NASA's Short Take Off and Landing (STOL) project, was designed to facilitate large and small, STOL and conventional aircraft using the same runway.

In the early 1970s, the PA-30, serial number 30-1498, was used to test a flight technique used to fly Remotely Piloted Research Vehicles (RPRV's). The technique was first tested with the cockpit windows of the light aircraft blacked out while the pilot flew the aircraft utilizing a television monitor which gave him a "pilot's eye" view ahead of the aircraft. Later pilots flew the aircraft from a ground cockpit, a procedure used with all RPRV's. TV and two-way telemetry allow the pilot to be in constant control of the aircraft. The apparatus mounted over the cockpit is a special fish eye lens camera, used to obtain images that are transmitted to the ground based cockpit. This project paved the way for sophisticated, highly successful research programs involving high risk spin, stall, and flight control conditions, such as the HiMAT and the subscale F-15 remotely piloted vehicles.

Over the years, NASA 808 has also been used for spin and stall research related to general aviation aircraft and also research to alleviate wake vortices behind large jetliners.

In November 1973, the PA-30 and an F-104 were used to measure the force and effects of wake vortices behind large aircraft using a three engine B-727. Smoke generators were placed on the 727 and the smaller aircraft followed to measure the vortices. This program directly influenced the later wake vortex tests on NASA's 747 using a T-37B and a Learjet as chase aircraft, which led to successful means of alleviating dangerous vortices.

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[iflightsim]

So what causes that tail to flutter so much? It looks like it's about to come off.

[airboyd]

Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, buildings, telegraph wires, stop signs, and bridges. Flutter occurs as a result of interactions between aerodynamics, stiffness, and inertial forces on a structure. This vibration can cause structural failure and therefore considering flutter characteristics is an essential part of designing an aircraft. See also the Tacoma Narrows Bridge failure.

[LethalHobo]

Thats not a Tail Flutter test, that PA-30 gets its thrust from flapping its tail like that, obviously!

[Scrapheap71]

So that's where brown stripes in underwear come from!!

[The2003roadking]

Did the aircraft smell like poo inside  after that test ?

[Bellerspitts]

what airplane{prop}can exceed vne in level fight? And for sale twin comanche.

[94z07]

@Davesintexas NASA test pilot wearing a parachute. (cabin door on quick release) No need to recall anything. The flutter was caused by deliberately flying well above Vne published in the POH.

[Davesintexas]

Who was crazy enough to test that plane like that? Well, cudos to them and was anything done on the design or recall? Thats gota be design flaw and recall time...that plane had no control under those circumstances

[davidlopresti]

this also happens in the single Comanches. LoPresti sells the beef up kit to help prevent flutter and raises,the Vne to 227 mph.

[LethalHobo]

@velophile this occurs below Vno normally, at a specific power/attitude/trim

[Ranzabar]

I'd a pooped my pants

[ziegle9876]

This is WAY beyond Vne, must be around 250kn+ indicated.

[Dominoes282]

At first I was like it's not that bad then I was like GTFO!

[BenHaor]

Scary!

[snoopyloopy]

@iflightsim very complicated equations and models come into play that i don't even want to look up right now. but basically, the horizontal tail begins to oscillate at the natural frequency. but instead of getting the oscillations damped, they become driven and get bigger each cycle.

[Ajennin3]

this happened to our plane last night from Atlanta to Chicago on Delta...SO SCARY

[3593893]

@MrComanche250 - That makes 2 of us.

[pinoyaggie]

@airboyd Very good explanation!

[nojyt]

Yes. To get the plane to flutter like this, they approach the maximum theoretical speed of the aircraft, way beyond VNE.

[MrComanche250]

This video scares the hell out of me

[velophile]

Is that what happens when you go past VNE? (Velocity Never Exceed) Hmm is that why we have VNE, VA, and all those different V-speeds?

[bruno84]

Thank you for posting this rare video!!

[bruno84]

@LethalHobo :D