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Post by Dave Homewood on Sept 17, 2022 22:14:42 GMT 12
For those here that have flown the de Havilland Devon, I was wondering, what is the aircraft like to fly if one of the engines quit? Does it happily fly OK on a single engine? Or is it a short matter of time before a forced landing?
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Post by Bruce on Sept 17, 2022 22:34:43 GMT 12
Actually, I've seen what Devon single engine performance is like - But with the dead prop unfeathered! Back in the early 1990s When I was working at Ardmore, We did a prop change on Civil Devon ZK-RNG. It needed a test flight to check the rigging, and in a somewhat illegal sort of arrangement I found myself onboard with the 2 crew and 2 or 3 other hangars - on. Out to the south of the Hunuas, the weather wasn't great, so we didn't climb very high but they went through the prop feathering test. Shutdown the LH engine and feather the prop. Unfortunately, the rigging wasn't quite right and the prop wouldn't feather. lots of drag and the aircraft started descending. Not only that, but the engine proved very reluctant to restart, and the aircraft, with all the extras onboard, was going downhill pretty quickly! being fairly low to start with we were getting down to less than 1000ft above the hills when the engine restarted! Learnt why test flights shouldn't be taken lightly from that one! Apparently however if the prop feathers OK, they fly alright, but as with any twin - if you cant feather, you have problems!
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jaybee
Squadron Leader
Posts: 122
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Post by jaybee on Sept 18, 2022 12:06:31 GMT 12
Dave, the RNZAF Pilots Notes say (p.32 - para 51(c)) that if engine failure occurs below safety speed, until such time as the flaps and undercarriage are raised and speed increased to 85 knots, a nose down attitude and loss of height must be accepted. Otherwise yes it can fly on one engine. CFL Jenks inASHNZ Vol 47 No 1 at page 19 said with one shut down height could generally be maintained if flown with care - but not if the undercarriage was down.
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Post by Antonio on Sept 18, 2022 12:40:35 GMT 12
Which engine powered the undercart?
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Post by Dave Homewood on Sept 18, 2022 12:43:57 GMT 12
Thanks Jaybee.
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Post by Peter Lewis on Sept 19, 2022 20:12:15 GMT 12
Most 'modern' civilian light twins can maintain height on one engine.
Older ones - eg DH84 Dragon - and you will be going downhill all the way.
The reality is that the most dangerous aircraft in the sky are light twins.
The popular saying is that the engine still running is there to get you to scene of the accident.
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Post by oj on Sept 19, 2022 20:47:06 GMT 12
I would like a bit more detail here.
Does the Gypsy Queen have a gated throttle that can be pushed into emergency power boost?
If so, for how long?
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Post by grant on Sept 19, 2022 21:32:26 GMT 12
I would like a bit more detail here. Does the Gypsy Queen have a gated throttle that can be pushed into emergency power boost? If so, for how long? No it didn't. Max power was set for takeoff (2800 rpm +6 lbs boost) for a max time of 5 minutes or 15 minutes for operational necessity. Max continuous was 2600 +5, or 2400 +2 with weak mixture Safety speed was 90 kts The flight manual says that at MAUW the aircraft should maintain height 5500ft at max cont 100-105kts, not 100% sure that was right much of the time. I was radio operator on several pilots ATPL check flights where an engine was shut down off the east coast, and it was a long haul back to to the coast at 100kts |
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Post by Dave Homewood on Sept 19, 2022 22:21:10 GMT 12
Thanks Grant.
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Post by mit on Sept 20, 2022 10:55:15 GMT 12
For those here that have flown the de Havilland Devon, I was wondering, what is the aircraft like to fly if one of the engines quit? Does it happily fly OK on a single engine? Or is it a short matter of time before a forced landing? Having had the most recent engine failure in a Devon in New Zealand I must say it flew beautifully. After hearing for years and years of how bad they are on one, I was relieved to find it very manageable and we climb to about 10,000feet before we need to start our descent, she was still climbing happily at that point. The problem came in RNZAF service that they were very heavily loaded with equipment, fuel and students/instructors on a typical mission (we removed over 900 lbs of wiring and surplus navigation equipment, that is excluding the cabin student station and equipment which had already been removed) Which engine powered the undercart? Both engines have a compressor and there are two completely seperate pneumatic systems, either of which can lower and retract the u/c, flaps and operate the brakes The Dehavilland safety speed is 80 kts, the RNZAF increase it to 90 kts, I can only assume they did this to standard the speed across the aircraft fleet, they did the same with flap speeds and U/C speeds |
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Post by tbf2504 on Sept 20, 2022 11:12:29 GMT 12
Having experienced an engine failure some 20 miles off the Canterbury coast when returning from a SAR mission off Kaikoura on a very hot summer's day, I can attest that a Devon in that circumstances with four on board
and the SAR droppables, even with a reduced fuel load descends gradually towards the sea!! Fortunately for us we stabalised at around 800' over the Bromley sewage works and made a single engine landing on the northwest
vector at Wigram (the last bit was a most interesting experience with only one shot at landing between Euclid tyres being positioned for the Lady Wigram Trophy race the next day, plus a MOWD truck that failed to hear
the tower or see the very pistol flares and careered right across our front at less than 10 yards! At this point all was shut down and we walked!)
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Post by grant on Sept 20, 2022 21:15:48 GMT 12
Having experienced an engine failure some 20 miles off the Canterbury coast when returning from a SAR mission off Kaikoura Funny, I was going to mention in my reply above about a SAR flight that had an engine failure and didn't level out until 800 ft. If it is the same one I was thinking of, it was late Jan 1979. My first day at Fly Flight and after a famil flight in the morning went out on a SAR which, if I remember correctly, was to replace the aircraft that came back with the failed engine.
i'm glad the safety speed was really 80kts, it sometimes seems ages before getting to 90kts on takeoff!
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Post by Dave Homewood on Sept 20, 2022 22:14:35 GMT 12
Some interesting experiences there guys, thanks Mit, Paul and Grant!
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Post by tbf2504 on Sept 21, 2022 8:45:33 GMT 12
The aircraft was NZ1803 (now in the museum) the pilot was Richard Francis, the Nav was the Operations Flight Commander and I was the stand-in Signaller and the date was 26 January 1979. Good memory Grant
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