I was looking to the left as I was just about to pull up to the vertical for the next figure which was a stall turn, so my eyes were on the sight gauge and horizon to the left.
I was not looking straight ahead at the time of the incident.
My first thought was 'Bird Strike' as I'd seen lots of gull's circling in thermals during the climb and during the first sequence earlier in the day. Fenland is quite close to The Wash so the coast is nearby and many sea birds are sharing the air.
There was a change in sound - a notable buzzing noise coming from the front of the aircraft. I immediately reduced the throttle to just above idle.
A quick glance at the engine instruments confirmed nothing untoward with the engine so the sound reinforced my first thoughts of a bird strike to the prop.
Although it could also be a loose piece of bodywork or fairing which was 'buzzing' in the airstream? I didn't know for sure but suspected the prop despite there being nothing different vibration-wise from normal operation.
A glide approach was then started back to runway 26 - which was the wind favouring runway of choice below. I was very fortunate as to where and when this incident happened BTW, high and fast (a high energy state) and right over an airfield with 2 runways.
A call was then made on the box frequency to the Chief Judge to let him know I had a problem and I was ending the sequence. He acknowledged and I immediately went to the airfield frequency which was blocked due to an incoming aircraft 5 minutes out making a long drawn out call. I took the time to eyeball my situation some more and visualise the approach to 26. Once the other traffic and the tower had stopped talking I made a Pan-Pan call, stating I had a problem and that my intention was an immediate forced landing on 26. The tower continued to talk back to me and also talked to me when on finals giving me wind information but I was mentally blocking out most of what he said as it was irrelevant at this stage and my brain needed to fully focus on the aviating from now on.
During the approach I verbalised to myself out loud "No go-arounds!". This acts as a sort of 'order' so your monkey brain does not take over and do something stupid. I often used this technique when I was Gliding - which if you have ever done in a competitive environment is just a series of decisions, the winning pilot usually having made the best decisions as flying skills don't count for nearly as much as good decisions in the results.
Coming onto the final approach and now lined up with runway 26 I again verbalised my situation and gave myself an order to correct. "Too high, too fast!" - "Side Slip!". So a side slip was engaged to lose the excess energy I had.
Once flap limiting speed was reached and the runway was certain to be 'made' I went for full flap. A final little side slip to lose that last bit of excess energy and then a reasonable landing was made with no further damage done.
Now comes the question - if you have an excess of energy then should you go for best glide, that is; fly slowly and extend your thinking time, or should you just aim to get back on the ground whilst things are in your favour - in this case an empty runway. More time would not have helped me in this case - if anything I have learned from this experience that taking excess energy down low is a good thing and a safety net - typically in an emergency you can always get rid of energy but not put it back. So if I were to do it again I would do the same thing.
Once I had reduced the throttle to just above idle I treated the rest of the flight as a glide approach - something I do often as practise anyway so I'm quite familiar with the 'picture', performance and sensations that go along with it.
Having said that - if for some reason I had to add some energy there was still the option to do that with the engine running but that would have been with some risk - still preferable to crashing into trees or water if that had been the other options though. ie: the risk was worth it if the other outcome was worse. As it was I had an excess of energy so did not need to ask anything of the powertrain after the incident.
I was asked "Why didn't you turn the engine off" by one pilot (the only one out of the hundred or so that have talked to me about the incident to ask such a question BTW). The answer to that is quite simple and 4 fold.
Firstly there was nothing wrong with the engine so shutting it down would not have 'saved' it from further damage (anyway engines can be fixed, people not so easily. As a pilot you should always be concerned with doing the least dangerous action to yourself rather than the least damaging action to 'some-thing').
Secondly the prop had been through the most intense energy state at the time of the incident, which was - high speed, high rpm. Once the throttle was reduced to just above idle and the airspeed reduced somewhat then the chances of the prop failing anymore was reduced to the point of 'highly unlikely'.
Finally and this is the main point, if I had shut down the engine then I would have had a completely unknown performance state to deal with that could not be altered and one that I had never practised (a dead stick) so this would have been very unfamiliar to me, which would have increased the workload and therefore the risk.
So the safest thing to do was to keep the engine running - albeit at just above idle as that is it's smoothest setting and provides the airframe with the least amount of drag - much less drag than a stopped prop would do.
It was only when I had taxied in and shutdown that the cause was confirmed - the prop stopped with the blade in front of me that suffered the most damage and was split. So it was confirmed as prop damage after all. At this point I suspected the spinner causing it and a friend coming up to shake my hand confirmed that with "the spinner is gone" (you cannot see the spinner from the cockpit of a Twister).
Luckily there was no other damage to the airframe as the spinner was disintegrated into thousands of tiny pieces which made there way either over or under the wings and tail. There is a very small scratch on the outside of the cowl but other than that I can find no other damage at all.
I had cleaned the spinner and prop before this flight too and did not notice any screws missing or anything else untoward so it is still somewhat of a mystery as to why the spinner failed in the first place. I would only add to this that the spinner was made by Hercules Propellers and was not a factory supplied item. It was made to a different schedule and was said to me (by a third party) to be 'not fit for purpose' (not their actual words, I am being nice here). I will do a separate post later on about the new and improved spinner I am working on as a replacement.
As usual I was filming the sequence from the tail looking forward so there is video of the whole event. Even though the damage itself happens in part of a frame - it happens that quick - from nothing untoward to prop damage in an instant, the video hopefully shows something someone else can learn from.
I edited the video to show what happened and how I dealt with it. I hope only that it informs others in some way. Check your spinners! And also practise your forced landings. If you found the 'Verbalising orders' thing helpful then think about employing it - one day it may help you make the right choices in a high pressure situation and not let your monkey brain take over.
To that final point there are many examples over the years of seemingly very experienced and capable pilots doing the 'wrong thing' in an emergency due to letting their monkey brain take over. The gentle pulling back on the stick 'I don't want to crash feeling after engine failure' (when it should be pushed forward) which results in a spin into terra firma.
Video on this link: https://www.youtube.com/watch?v=3n3QydcF0-I
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| The leading edge urethane material stayed together - despite hitting the spinner at approx 600 mph and then the prop split along the next weakest point back which is where the urethane is attached to the wood. |
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| There is a small notch in the urethane which shows how much force is going on as you can hit this material with an axe and it does nothing normally. |
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| No other damage to the airframe, so no harm done except to my wallet and total score in the competition. Second place was on the cards again until this happened. |
