Latest AAIB Bulletin

I am sorry to hear it was a friend in the Towcester accident.

We have removed the Russian radio and ADF from the back of the aircraft, and replaced them with some flate metal plates. This allows us to see down to the tail clearly. We also have a policy of making sure passengers have empty pockets, and we wear flying suits, not for show but because of the zipped pockets, and a knee pad to write on. We also check the aircraft for FOD before and after each flight.

After the ceconite bulhead had been fitted, I removed the side panel at the tail, and felt around and found screws, and bits of tie-wrap. You would have thought the maintenance organisation would have made sure there was no rubbish before putting in the bulkhead!

“We also discussed control restriction, coming off a stall turn unable to pull up what would you do?

Push forward? In the heat of the moment probably not, but having thought about and discussed it on the ground, yes you may well do. I know we have a ceconite bulkhead now, but these are not completely fool proof. “

This is a question which has resonance for me as a school friend had a share in the Yak which went down near Towcester with the mystery screwdriver, and the other Southend Yak had the mobile phone jam the controls.

The pilot in the back seat of the Southend Yak was a member of our group, and I asked him why he wasn’t wearing a parachute. “I’d sent it for repacking and didn’t think it would matter for once,” was his reply. Fortunate or what?!!

Two dead and two very lucky and an aircraft flying again. I think with this scenario it all depends on height. The Southend guys had climbed another thousand feet before doing the next batch of stall turns. That’s what saved them. The phone had been sitting in the aircraft for some time, and clouting the underside of the rear fuselage pre-flight hadn’t shifted it.

Our new Yak has got a clear inspection panel under the tail, but it would have been no use in this case.

This is what’s great about the internet – you can learn so much. I’ve just been reading on a thread PPRuNe about RAF Meteor casualties. Yaks are really safe to fly!!!

YR

Yakrider
“Fortunately I’m a little bit older and a whole lot wiser now. And hopefully others can learn from this too. If it gives someone a few more seconds to decide what the best option is if it happens to them, then at least something positive can be gained from it all”
I agree, by discussing possible failures and what to do about them helps when it actually happens to you. The first plug failure in our Yak, lead to smoke and the smell of burning as the HT lead melted on the exhaust. Fortunately the pilot was close to base and returned safely. When the plug went bang on me, it was as the US article had said, and I also returned safely. The last time, the plug that blew was on the CHT sensor cylinder, and the sensor heated up and showed the CHT off the gauge, a precautionary landing in a field damaged the aircraft, but both occupants were okay.

We also discussed control restriction, coming off a stall turn unable to pull up what would you do?
Push forward? In the heat of the moment probably not, but having thought about and discussed it on the ground, yes you may well do. I know we have a ceconite bulkhead now, but these are not completely fool proof.

At the time everyone was convinced that the cause was contaminated fuel. From the report, they did look for it but found nothing except the blown plug. Certainly at the time, the only thing I could think of, from what was happening, was that there was a fuel or carburettor problem. Which is why I was pumping the primer.

What still amazes me is that there is still no systematic information available on plug failures. I have gleaned what information I could over the past two or three years by trawling the internet, but nothing I had read was remotely similar to the actual symptoms I experienced (as opposed to merely saying that the engine lost power) until I saw the article in TP after the event.

When I first heard it was a plug, I was very dubious as nothing seemed to add up. The Americans had done a test where they removed two plugs completely (including one from Number 6 cylinder also at the bottom of the engine) and started and run the engine without major problems. Other anecdotal descriptions I had heard from other people seemed to suggest it was a non event. So, I felt that I must have done something wrong. The TP article explained a lot and took a whole weight off my mind.

Fortunately I’m a little bit older and a whole lot wiser now. And hopefully others can learn from this too. If it gives someone a few more seconds to decide what the best option is if it happens to them, then at least something positive can be gained from it all.

Janie: Not seen the ghastly remains recently, but they were already using bits to patch up other aircraft when I saw it last. So, in a way, it will still be flying!

The replacement – Charlie Tango – was up there last week having its annual, so you might have seen that silver and blue jobby too!

YR

Yakrider, as a fellow Yak pilot I am glad you are well. I posted at the time, from the information given I thought it was a plug failure. However Moggy decided to remove the post as it was worded such that I might have affended you ( not bitching Moggy).
We have had three plug failures in our Yak, hence Tim was able to get his Yak repaired at Sywell so promptly.
I believe every Yak radial pilot should read an article published in the USA after a plug failure caused a Yak 52 to stall and spin in. It was available on a web site but that is now defunct. However I will email the article to anyone interested.

Glad to hear you’re fine, certainly an interesting and informative read.

Do you think the helmet would help in the like of the usual Spamcans?

dme

I can recommend Campbell Aeroclassics helmets. Soft-helmet look, hard-helmet practicality.

YakRider: I don’t know if you have seen your old fusilage lately, but when I get around to downloading my pics, I’ll send you a copy.

Glad to here you are on the mend, i to hasd an accident several years ago in a Tiger Moth. Had i not been wearing a bone dome i would not be placing this post now!! Many people decry the use of bonedome’s, particularly in vintage aeroplane’s, because they say they look naff! or that they are expensive. You only have one head!!! protect it!!!
Again glad to here you are on the mend and maybe more will lean from these accidents and invest in a bonedome.

I was indeed my five minutes of fame. The helmet certainly saved my life, as I hit my head hard enough on the instrument panel to split the bonedome on both sides at the front. I wasn’t aware of this until I got home from hospital and examined the helmet when I was putting together my statement for the AAIB.

I did spit out a couple of broken teeth and the chinstrap had gashed my chin, but I assumed at the time that I had perhaps struck the stick. Fortunately the helmet was insured, so will be replaced. The aircraft has been replaced too, and was due to be collected yesterday, so hopefully I shall see it for the first time today.

I was reading a book recently by a Seafire pilot, who said that when naval aircraft missed the arrestor wires and ran into the barrier, the pilot experienced deceleration forces of around 20G. As the Yak stopped in about 40 feet, I must have experienced something of similar magnitude. Several medics have said I was extremely lucky as the chest injuries I suffered are often fatal. The Yak is an immensely strong aircraft, which must have helped my survivability!

The whole affair has been an huge learning exercise for me, trying to analyse and explain what happened and what I could have done differently or better. The irony is that there was an article in Today’s Pilot about a similar incident a couple of months ago, which if I had been able to read before my engine failure, it would have explained exactly what was happening – though of course you still have the problem of getting back on the ground in one piece.

The really confusing thing was that the engine instruments were all in the green, while the engine was cutting, picking up again after an interval then cutting again. We all train to deal with engine failures, but the assumption is that the engine stops. In this case, it kept running intermittently, which certainly complicates one’s though processes in trying to work out what’s going on, fly the aeroplane (and in my case get back over dry land) and tell people you’ve got a problem.

There have been discussions about plug failures on other bulletin boards, and I think it would be useful if information could be collected about the different symptoms of plug failures (which can involve cooking the cylinder head temp sensor and giving a false reading in the red, or setting fire to the ignition harness – neither of which happened to me), and what to do if it happens. I have not seen any mention of plug failure in any emergency checklists for the Yak, yet this is the most likely scenario for engine problems rather than a complete mechanical failure.

The mention by the AAIB that mini haydraulic locks can also damage plugs is worthy of note, as such damage is insidious and could take months to manifest itself. I was talking to someone recently who serviced tank engines during the war. American tanks were powered by radial engines, and he said that if they had a hydraulic lock they would change the plugs as a matter of course.

Of course Yaks in their original environment were maintained on a military basis, and the same probably applied. Now in civilian hands, and with less operational knowledge, it is easier for these potential problems to slip through unremarked.

Hopefully other people can learn from what happened to me. Certainly regarding the helmet, if it gives pause for thought to someone flying similar types of aircraft then other lives might be saved.

The doctors all say I’m now fit to fly, and I’m just waiting for the CAA to agree. As I spent last week working on a project in the Lake District, and spent Thursday walking 8 miles and doing 2500 feet of ascent and descent as well, I certainly feel I’m now fit again.

YR