Saw a very interesting show on Discovery tonight about crash investigators. There was a story about a prop plane that crashed because flutter caused the turbo prop engine to rip off the plane and cause a catastrophic crash.

Does anyone here have any knowledge as to how modern planes are protected from flutter? Watching the video it's very scary as to how flutter can literally shake a plane apart...

They fly it to see whether it flutters, and if it does, they redesign it.

That's quite a frivolous way of putting it, but this is from this week's Flight Internationa regarding the 777-300ER which is starting its flight test programme:-

OK, this is from my aircraft manuals.

"At high speed some control surfaces have a tendency to 'flutter'. This is a vibration that results from the changes in pressure distribution over the surface as its angle of attack is altered.

"If part of the structure starts to vibrate (and control surfaces are particularly susceptible to this) then these oscillations can quickly reach dangerous proportions. To avoid this tendency to flutter, the designer needs to alter the mass distribution of the surface.

"The aim of mass-balancing is not for the control to be balanced in the sense of remaining level, but to alter the mass-distribution of the control to avoid any flutter or vibration.

"The mass balance is placed forward of the hinge line to bring the Centre of Gravity of the control surface up to the hinge line or even slightly ahead of it.

Acknowledgement - The Aeroplane Technical, by T. Thom.

So that's how "modern" planes are protected from it. Even the little Cessna I fly has this (and I could be asked about it on my Private Pilot's test). It's really a resonance/harmonics calculation for each control surface, including the wings. If you fly old biplanes you can sometimes see this vibration in the bracing wires betwen the wings.

I'm guessing that the TV programme you saw was about the Lockheed Electra around 1960. You are probably asking how the flutter problem showed up so early in its life and how Lockheed never found it during design or testing. That's what the aviation professionals at the time asked, too ....

(Edited for typo)

[This message has been edited by WHBM (edited 01-30-2003).]

You probably saw show about the Lockheed Electra, which had the flutter problem you describe. That was a plane that was designed well over 50 years ago -- before aircraft designers had the computer crunch power to run the comprehensive mathematical models that are necessary of analyze the complex interactions of aerodynamics and structural dynamics. The problems with the Electra were eventually solved, and the aircraft is now the basic of the P-3 Anti-submarine patrol aircraft.

With today's understanding of the physics, the computer power to analyze the designs, and the ground and flight testing required before certification, the chances of flutter problem on a current or future commercial airliner are virtually nil.

Actually the show I saw was about a more recent plane crash. It was a cessna or beechcraft type of small turbo prop where a flight trainer and 2 pilots died. The NTSB wrote the accident off as pilot error. The flight trainer's wife didn't concurr and did some investigations, and thanks to computer analysis of the cockpit voice recorder, where the 4th channel eerily recorded in a round about way the power of the engine, let investigators to deduce that the right engine had suffered catastrophic flutter.

The right engine shredded off the right wing, and took of part of the tail with it. The pilots never had a chance to recover. Then Discovery showed some flutter problems on model airplanes as well as long wing span gliders. It was incredible to see a model just shred itself to pieces in the space of a few seconds.

I'm normally not too bothered by turbulence, but I didn't know about flutter. It's good to know that flutter is minimized these days by good design...