Sorry to see that an Aztec that made a forced landing in Trent Park Enfield (the Sassoon family estate which held high ranking German officer prisoners in WW2), has been removed from the CAA register.
I operated an Aztec in the distant past and it was a loyal, dependable aircraft, requiring uneconomic amounts of maintenance.
I find it hard to understand, if the pilot/operator successfully feathered the engine with the failed cylinder, how the aircraft failed to maintain altitude. Allowing the engine to seize due to oil starvation before feathering would be a more realistic scenario, for failing to maintain the SE ceiling of 5,000 feet in drift down. The aircraft also overflew Southend, Stapleford, and North Weald. The aircraft was at FL90 near DET when the oil leak occurred so the airmanship is a bit odd. In CAS a PAN was declared but then the pilot decided to continue to Wellesbourne Mountford over 100 nm away, even though ATC helpfully offered a priority to Southend!
The trusty IO-540s were flying on condition beyond their TBO. If it wasn’t poor airmanship or poor asymmetric technique due to poor currency in asymmetric operations, then it was trying to fly single engine with past their sell by date engines.
I fear this confirms my opinion of MEPs operated privately: there is a real risk the operator is not investing in keeping these aged, complex machines maintained to the required level so that the twin engine/system redundancy, and pilot currency, delivers design performance.
The good news is no one was injured, except indirectly on the annual insurance premium for other GA operators.
I find it hard to understand, if the pilot/operator successfully feathered the engine with the failed cylinder, how the aircraft failed to maintain altitude.
Reduced power on the remaining engine seems to be the answer but the 19% reduced power dyno test result on the functioning engine seems a little high. Four of 6 cylinders had good cam profiles, leak-down was good on all cylinders tested and the inlet cam lobe for cylinders 1 & 2 had 50% reduced lift with power typically reduced less than in proportion to reduced lift, its more like the remaining area under the lift-time curve.
Anybody who has used multiple dynos on the same engine knows that no two give the same reading.
if the pilot/operator successfully feathered the engine with the failed cylinder, how the aircraft failed to maintain altitude. Allowing the engine to seize due to oil starvation before feathering would be a more realistic scenario,
The after-landing photo of the aircraft in the accident report clearly shows a feathered left prop and an unfeatered (and damaged) right prop, so it was definitely feathered.
The density at 5,000ft is 14% lower than at sea level, so it appears the Aztec needs around 85% of engine power at its SE service ceiling; so if it only delivered 81% (or even 85%) at sea level, ending up in a field was a inevitable.
While the decision making was certainly questionable, I guess that this was the likely outcome regadless. Even if he had diverted to Southend he would probably have found out he could not maintain altitude somewhere on base leg and ended up in a field on or close to final.
Even if he had diverted to Southend he would probably have found out he could not maintain altitude somewhere on base leg and ended up in a field on or close to final
I gather flying ILS 3deg (IMC) is possible on one engine? Yes flying circuit in Southend would have resulted in same outcome as circuit in Elstree…talking to ATC does not change much other than getting instant SAR on crash
I am very puzzled by routing to Westbourne tough, Stapleford to Elstree at 2000ft on one engine? it would have been easy to fly Southend-Cambridge, that is likely to give 40min-80min of flying from 8000ft, still tight but keeps height available rather than slam-dunk in DET or cross over London (going to Southend is the easy and safe option)
Looking at the report, I think the owner wasn’t regularly flying/training N-1, otherwise he would have detected that a single engine wasn’t sufficient to maintain flyability,
It’s a pity because you go twin because of that, and finally don’t have it when you need it.
I wonder if training 1pob or 2pob was fine*? then 4pob near MTOW? the changes of GC & MTOW between (light) training and (heavy) actual flying does make lot of surprises in handling
*fine as in keeping level rather than climb like a rocket with +500fpm on one engine
In flying school on DA42, we usually train near MTOW and climb is still possible (100-300fpm @ 5000ft depending on planes), but this is easy to reach MTOW (3POB + full tank).
Interesting, how would you determine if BOTH of your piston engines are fine? Look at the FF on your fuel totaliser, if you have it?
Otherwise it would be almost impossible to say if your aircraft is doing 100% power on takeoff ( (100%+100%)/2) or only 90% ( (100%+81%)/2).
Reading the article my forehead wrinkles.
Ok, decision making was bad and on single engine failure not to land asap with so many good options around wouldn’t be my SOP.
But, reading the right engine scored 81% on the dyno test, means it was virtually dead and that should have been discovered earlier by the pilot or at latest the maintenance shop. I remember there was a US test on some university, where they tried to get facts on the compression myth, for which they had to remove the piston rings to get the engine down to still about 90% power (wrecking in minutes due to oil loss, but still going strong).
Btw, I welcome the inherent criticism on Part-ML in the report. When it came into place, I had a discussion with my engine and maintenance shop, which tried to sell the easier rules, on engine maintenance and I insisted on keeping the procedures we set in place earlier. At the time I was running a 50 year old airframe with 15 years SMOH nearing FHBO and we had set up an advanced control system to check also for corrosion. Yes, we did change cylinders due to that and reading the report, it feels as if we did the right preventive thing. Btw, when we finally did the OHs 300 FH and 15 years beyond limits we found quite extensive thingies, which let us suspect the OH before was more or less minimum effort for zero papers and selling, so the engines had most probably 4500 FH between real OH.
Anyways, 43 years old engines, even if not flown that much, are an example why we should set up an ‘aging aircraft initiative’ as the FAA did? Yes, I know of the bullsh*t happening with famous SID interpretation of European NAAs and my aircraft at the time was subject to that BS, but one could do the right thing without being an a*hole, even in Europe.
About flying on to unsuitable destinations: I lost a friend to this. The thing is, he was an older guy with generally good judgement (and many thousands of hours of incident-free flying to show for it). He went on a camping trip with a friend (also multiengine rated) in his Apache – not a great single engine performer – had an engine failure in cruise flight at 5000ft+ and overflew a number of airports – trying to press onto a destination we’ll never know, but ended up having to make a forced landing in a small field which ended in trees, killing both of them.
It seems so bizarre to all of us who knew him. It was in the USA too, so the thought of “if I’m stuck at [big airport] I will run up thousands in landing, handling and parking fees while my plane gets fixed” wasn’t a factor here.