Centaurus
10th May 2013, 13:30
In the June 2013 issue of "Aeroplane" magazine under the section called Q&A (Questions and Answers), a contributor asks about a Lincoln crash in 1946 where shortly after take off one engine failed, rapidly followed by failure of all the other engines. Seems similar accidents occurred to two other Lincolns of that era. The contributor wanted to know why the engines failed almost simultaneously and heard it may have had something to do with low pneumatic accumulator air pressure (the same pressure that operated the brakes).
Reference to "Pilot's and Flight Engineer's Notes" for Lincoln Mk 1 and 2 (A.P.2847A&B-PN dated June 1947) is relevant to the question. Page 15 under para. 25, sub-heading Slow-Running Cut-Off controls. The slow-running cut-off's which are used for stopping the engines, are operated by electro-pneumatic rams controlled by four switches on the right-hand side of the instrument panel just above the engine starter pushbuttons. The switches must be held in the down position to put the controls into the idle-cut-off position.
If MOD 1789 has not been incorporated, the slow-running cut-out switches are not spring loaded and will stay in idle-cut-off (down) position when set there. The up position is marked Engine On. If the pneumatic supply pressure is less that 160 PSI it is possible to start the engines with the slow-running-cut-off switches in the idle-cut-off position (if MOD 1789 has not been inorporated: then, when the supply pressure builds up the idle-cut-off rams will operate and all four engines will stop .
............................................................ ....................................
The loss of the three Lincolns due apparently to simultaneous failure of all four engines intrigued me and brought back memories of my time as a pilot on Lincolns in Australia. In those days (the 1950's) instructors from the RAAF Central Flying school would visit various units and conduct random flying tests on squadron pilots to check the general standard of flying. On one of these visits I was tested by a Flight Lieutenant Denis Smallbones who was on exchange from RAF CFS. He was a former wartime Spitfire pilot and a truly delightful chap but with only a few hours on Lincolns at CFS.
I briefed him on the operation of the slow-running-cut-off switches since he was responsible for starting the engines from the right hand dicky seat position. Now with our Lincolns, once the throttles were at full power it was not possible to `fail` an engine by cutting the mixture control. (The mixture control being the slow-running-cut-off switch.) To stop the engine its throttle had first to be closed to idle and only then would the slow-running-cut-off switch operate. Other than that the only the only other way to simulate an engine failure was either by pulling back the throttle or shutting off the engine main fuel on/off cock. Of course shutting of the fuel cock caused a real engine failure.
So shortly after lift-off, the CFS instructor decided to give me an engine failure and operated the No 1 slow-running-cut-off switch to idle-cut-off. Of course nothing happened just like I told him earlier. He had forgotten about this - although this was understandable, since the Lincolns he had flown at CFS were un-modified and operation of any slow-running-cut-off switch to cut-off would indeed stop the engine from operating. He then frightened the hell out of me by proceeding to laugh gleefully as he played with the four switches like a piano switching them on and off to prove I was right or wrong. All at 500 feet after take off. Not good airmanship to say the very least.
I was tempted to give him a spray but thought better of it. Rank had its priviliges and I was only a lowly 21 year old Sergeant Pilot, he was in command as well as being an officer and a gentleman of commissioned rank AND he had flown Spitfires against the enemy in WW2 and in my eyes he was a demi-God - lbeit a bloody stupid one... Fortunately the ICO switches worked as advertised and all engines kept going.
The years passed and I heard that Flight Lieutenant Denis Smallbones RAF had retired to live in Australia and became an Anglican vicar. Maybe in his own way he was thanking God for not smiting him (and me) down if those ICO switches had failed in their operation and we had lost all four engines and I wouldn't be writing this story now!
There were several accidents on Lancasters during WW2 caused by multiple uncommanded feathering of propellers. In his book "Flight of the Halifax", Captain G. Wikner, a civilian ferry pilot engaged in ferrying Lancasters in England, described one such incident. He and his flight engineer decided to test the feathering of each engine in turn while cruising at 3000 ft.
He wrote (edited for brevity): "No 4 starboard airscrew was feathered according to procedure. Power was increased on No 1 and 2 engines. No 3 airscrew was then feathered and now we were flying on two engines. In one minute I told the engineer to unfeather No 3 airscrew and watched him carefully. I was watching the RPM counter when I felt a sudden swing to port and looked out to see both airscrews feather and stop. The engineer then unfeathered No 4, the motor ran for a short period and finally cut out with a loud explosion as though short of fuel. While this happened, No 3 feathered itself with the result there were no engines functioning and I had control of an overgrown glider of about 30 tons. The wind was whistling around the aircraft and the rudders were inefficient.
I unfeathered No 1 and 2 airscrews then instructed the engineer to put on the booster pumps and change tanks. While this was happening I think the engineer was endeavouring to get No 3 unfeathered again- and then No 1 feathered itself. During all this motor juggling I had difficulty in maintaining a straight course, having to spin the rudder trim to one side or the other to meet the altering directions. I finally got No 1 unfeathered and running - this gave me two motors operating on the port side and two dead, wind-milling motors on the starboard. Skellingthorpe was within approach distance. I decided to leave the airscrews as they were fearing they might all feather again and went in for the landing. When I finished my run all four motors were ticking over.
I never heard what caused the trouble so I guessed it was hushed up. After my episode I learnt that four Lancasters had crashed at different times and all the crews killed. Investigators found the airscrews in the feathered position, so I believe the blame and the deaths of all the crew members should rest heavily on the shoulders of the aircraft factory"
............................................................ ........................................
Now to cap off this story. In 1996 I read a story in a Sydney magazine by the sole survivor of wartime Lancaster crash in 1942. His name was Chris Jarrett. Recounting his experience, he said: "It was a low level night flight into Germany, but a problem developed over Northern France. For some reason one engine stopped. The pilot told the engineer to feather it. He pressed the button to feather this particular motor and all four engines feathered off the one button. It left us with nothing but a full bomb load and plenty of petrol, so we just went down. I baled out through the front hatch...and the plane went over a small hill and blew up".
............................................................ ....................................
And that is the end of this story except to add one more thing to the mystery of the feathering props. I was an instructor on Lincolns in 1959 when an engine fitter told me he could feather two engines with the press of one button. I disbelieved him so he bet me ten pounds (or was it dollars then?)he could do it. We climbed into the Lincoln cockpit and after careful fiddling with a section of one feathering button and with the two left engines running, he pressed one of the buttons. Both engine propellers immediately feathered. I lost my ten pounds. Later I discovered why both propellers feathered with only one button actuated. But that is a story for another time...
Reference to "Pilot's and Flight Engineer's Notes" for Lincoln Mk 1 and 2 (A.P.2847A&B-PN dated June 1947) is relevant to the question. Page 15 under para. 25, sub-heading Slow-Running Cut-Off controls. The slow-running cut-off's which are used for stopping the engines, are operated by electro-pneumatic rams controlled by four switches on the right-hand side of the instrument panel just above the engine starter pushbuttons. The switches must be held in the down position to put the controls into the idle-cut-off position.
If MOD 1789 has not been incorporated, the slow-running cut-out switches are not spring loaded and will stay in idle-cut-off (down) position when set there. The up position is marked Engine On. If the pneumatic supply pressure is less that 160 PSI it is possible to start the engines with the slow-running-cut-off switches in the idle-cut-off position (if MOD 1789 has not been inorporated: then, when the supply pressure builds up the idle-cut-off rams will operate and all four engines will stop .
............................................................ ....................................
The loss of the three Lincolns due apparently to simultaneous failure of all four engines intrigued me and brought back memories of my time as a pilot on Lincolns in Australia. In those days (the 1950's) instructors from the RAAF Central Flying school would visit various units and conduct random flying tests on squadron pilots to check the general standard of flying. On one of these visits I was tested by a Flight Lieutenant Denis Smallbones who was on exchange from RAF CFS. He was a former wartime Spitfire pilot and a truly delightful chap but with only a few hours on Lincolns at CFS.
I briefed him on the operation of the slow-running-cut-off switches since he was responsible for starting the engines from the right hand dicky seat position. Now with our Lincolns, once the throttles were at full power it was not possible to `fail` an engine by cutting the mixture control. (The mixture control being the slow-running-cut-off switch.) To stop the engine its throttle had first to be closed to idle and only then would the slow-running-cut-off switch operate. Other than that the only the only other way to simulate an engine failure was either by pulling back the throttle or shutting off the engine main fuel on/off cock. Of course shutting of the fuel cock caused a real engine failure.
So shortly after lift-off, the CFS instructor decided to give me an engine failure and operated the No 1 slow-running-cut-off switch to idle-cut-off. Of course nothing happened just like I told him earlier. He had forgotten about this - although this was understandable, since the Lincolns he had flown at CFS were un-modified and operation of any slow-running-cut-off switch to cut-off would indeed stop the engine from operating. He then frightened the hell out of me by proceeding to laugh gleefully as he played with the four switches like a piano switching them on and off to prove I was right or wrong. All at 500 feet after take off. Not good airmanship to say the very least.
I was tempted to give him a spray but thought better of it. Rank had its priviliges and I was only a lowly 21 year old Sergeant Pilot, he was in command as well as being an officer and a gentleman of commissioned rank AND he had flown Spitfires against the enemy in WW2 and in my eyes he was a demi-God - lbeit a bloody stupid one... Fortunately the ICO switches worked as advertised and all engines kept going.
The years passed and I heard that Flight Lieutenant Denis Smallbones RAF had retired to live in Australia and became an Anglican vicar. Maybe in his own way he was thanking God for not smiting him (and me) down if those ICO switches had failed in their operation and we had lost all four engines and I wouldn't be writing this story now!
There were several accidents on Lancasters during WW2 caused by multiple uncommanded feathering of propellers. In his book "Flight of the Halifax", Captain G. Wikner, a civilian ferry pilot engaged in ferrying Lancasters in England, described one such incident. He and his flight engineer decided to test the feathering of each engine in turn while cruising at 3000 ft.
He wrote (edited for brevity): "No 4 starboard airscrew was feathered according to procedure. Power was increased on No 1 and 2 engines. No 3 airscrew was then feathered and now we were flying on two engines. In one minute I told the engineer to unfeather No 3 airscrew and watched him carefully. I was watching the RPM counter when I felt a sudden swing to port and looked out to see both airscrews feather and stop. The engineer then unfeathered No 4, the motor ran for a short period and finally cut out with a loud explosion as though short of fuel. While this happened, No 3 feathered itself with the result there were no engines functioning and I had control of an overgrown glider of about 30 tons. The wind was whistling around the aircraft and the rudders were inefficient.
I unfeathered No 1 and 2 airscrews then instructed the engineer to put on the booster pumps and change tanks. While this was happening I think the engineer was endeavouring to get No 3 unfeathered again- and then No 1 feathered itself. During all this motor juggling I had difficulty in maintaining a straight course, having to spin the rudder trim to one side or the other to meet the altering directions. I finally got No 1 unfeathered and running - this gave me two motors operating on the port side and two dead, wind-milling motors on the starboard. Skellingthorpe was within approach distance. I decided to leave the airscrews as they were fearing they might all feather again and went in for the landing. When I finished my run all four motors were ticking over.
I never heard what caused the trouble so I guessed it was hushed up. After my episode I learnt that four Lancasters had crashed at different times and all the crews killed. Investigators found the airscrews in the feathered position, so I believe the blame and the deaths of all the crew members should rest heavily on the shoulders of the aircraft factory"
............................................................ ........................................
Now to cap off this story. In 1996 I read a story in a Sydney magazine by the sole survivor of wartime Lancaster crash in 1942. His name was Chris Jarrett. Recounting his experience, he said: "It was a low level night flight into Germany, but a problem developed over Northern France. For some reason one engine stopped. The pilot told the engineer to feather it. He pressed the button to feather this particular motor and all four engines feathered off the one button. It left us with nothing but a full bomb load and plenty of petrol, so we just went down. I baled out through the front hatch...and the plane went over a small hill and blew up".
............................................................ ....................................
And that is the end of this story except to add one more thing to the mystery of the feathering props. I was an instructor on Lincolns in 1959 when an engine fitter told me he could feather two engines with the press of one button. I disbelieved him so he bet me ten pounds (or was it dollars then?)he could do it. We climbed into the Lincoln cockpit and after careful fiddling with a section of one feathering button and with the two left engines running, he pressed one of the buttons. Both engine propellers immediately feathered. I lost my ten pounds. Later I discovered why both propellers feathered with only one button actuated. But that is a story for another time...