Re; The Yaks. If it was last week (Monday-Wednesday), you saw the Aerostars working up for the new season. The week before it was the formation flying school at North Weald.

Here are a few pics of the Aerostars on Wednesday, just before a thunderstorm came through!

YR 😀

What’s that giant one behind?!

YR

The North Weald Cat has Avalon Aviation logos overpainted in orange, so you are most probably right.

YR

Another way that enormous strees can be put on an airframe is by using large deflections of the controls. The speed at whch significant damage can be done is well within the normal speed range for most non-aerobatic light aircraft. Remember the Airbus that crashed in New York because the fin detached after extreme rudder deflections caused by wake turbulence.

This link is to the accident bulletin of a PA28 Arrow, which suffered a catastrophic structural failure because of this.

http://www.dft.gov.uk/stellent/groups/dft_avsafety/documents/page/dft_avsafety_025533.hcsp

The scenario that the AAIB believe was the most likely is that the front seat passenger inadvertantly moved the controls and the pilot then reversed them.

I fly an Arrow, and was surprised by how much below the normal cruise speed of 130 knots one had to be to avoid structural damage – 118 knots, in fact. Should have known, of course.

There was another case of structural failure of a Commander 114, which flew into a snow storm and ended up diving into the ground after the wings came off as the pilot tried to recover from the dive. The manufacturers estimated the g load at the time of failure to be 8.8g. The link is at:

http://www.dft.gov.uk/stellent/groups/dft_avsafety/documents/page/dft_avsafety_500069.hcsp

I also fly a Bulldog, which has 8 g meters for monitoring the Fatigue Index, as well as a resettable one on the instrument panel. These have to be logged after each flight, along with the number of crew, number of take offs and landings and the total time. These are analysed annually and the remaining FI is calculated. Once that is used up, the aircraft stops flying and will have to be resparred.

At least with the meters, you know if you’ve pulled too much. And you cannot hide the fact from other people, because the FI meters cannot be reset. This has the advantage over the average club plane, where you can never be too sure what the last person to fly it had done.

YR