Spitfire/Seafire with contrarotating props

[stilton]

Does anyone know if it was possible to feather one of the props on these particular aircraft ?

[NutLoose]

Does anyone know if it was possible to feather one of the props on these particular aircraft ?

No, they are both driven off the engine, in fact you cannot feather any Spitfire prop, there is no point, if the engine fails you are going down and a feathering prop and all the gubbins would just add weight.

The only advantage of feathering is on a twin or more to reduce the drag on the failed engine and to limit damage to it so the other engine can keep you flying.

I do believe there is a Seafire floating around with the facility, but that is because they fitted an ex Shackleton engine, so as it had the facility they added it. On that you would feather both as if you could do only one the other would still be causing drag and trying to turn the engine… see


https://www.thegrowler.org.uk/avroshackleton/shackleton-data.htm

..

[DHfan]

Unlike the props fitted to the Gannet, the Spitfire/Seafire propeller is one single prop, not two separate items.

[Jhieminga]

I do believe there is a Seafire floating around with the facility, but that is because they fitted an ex Shackleton engine, so as it had the facility they added it.
Seafire FR.47 VP441 (http://www.warbirdregistry.org/spitregistry/seafire-vp441.html) has that option. As you stated it uses an ex-Shackleton engine and the feathering option was also retained because it can cut down on the drag. Some of the contra-prop Reno racers found out the hard way that six blades in full-fine produce a lot of drag (perhaps it was just Red Baron, I can't remember the details right now).

PS890 (http://www.warbirdregistry.org/spitregistry/spitfire-ps890.html) also flew with a contra-prop for a while, I don't know if it had a feathering option at the time. It has since been restored to a standard five-bladed prop.

[bean]

Unlike the props fitted to the Gannet, the Spitfire/Seafire propeller is one single prop, not two separate items.
The clue is in the Gannet powerplants name. Double Mamba
each part of the double drove its own prop

[treadigraph]

PS890 (http://www.warbirdregistry.org/spitregistry/spitfire-ps890.html) also flew with a contra-prop for a while, I don't know if it had a feathering option at the time. It has since been restored to a standard five-bladed prop.

It did have the feathering option, Steve Hinton fitted the Griffon 58 at Chino and, after his crash in the Red Baron Mustang at Reno in 1979, wasn't keen to repeat the experience of a six bladed airbrake adorning the front end in the event of an engine failure. It was great to see and hear it at Duxford a couple of times before the Griffon 65 was fitted.

Two Seafire FR.46s on rebuild in the UK, the one at Old Warden looked to be making fairly good progress last I heard of it. Also another XVII and an XV I believe.

[DuncanDoenitz]

You have one engine; why would you ever want to feather half the prop? (Or, indeed, have differential pitch in any mode of operation).

[DHfan]

PS890 was easy to pick out during the massed Spitfire takeoffs at Duxford - it went up like a lift!

[treadigraph]

PS890 was easy to pick out during the massed Spitfire takeoffs at Duxford - it went up like a lift!

Hinton had planned to go for a class brakes off to climb record in it - the contra props eliminated torque meaning he could get off the ground quickly; however some smart-ass* set the record beyond anything the Spitfire could achieve!

*Can't remember who or what, memory says it was an aerobatic type on the US airshow circuit around 2000...

[chevvron]

Hinton had planned to go for a class brakes off to climb record in it - the contra props eliminated torque meaning he could get off the ground quickly; however some smart-ass* set the record beyond anything the Spitfire could achieve!

*Can't remember who or what, memory says it was an aerobatic type on the US airshow circuit around 2000...
Can be tricky though.
During the maiden flight of the Hughes XF11 flown by himself, the rear prop of the right hand engine went into reverse due to a hydraulic leak and the aircraft crashed.

[Jhieminga]

The Griffon 58 with Shackleton props is a design with many miles on it. In that respect it is not a bad choice for a record attempt. The Hughes XF-11 used a familiar powerplant (the R-4360) but with a troublesome new prop arrangement. There is probably a good reason that they went with conventional props on the second XF-11.;)

[CAEBr]

The clue is in the Gannet powerplants name. Double Mamba
each part of the double drove its own prop

Yes, an interesting installation looking back. Probably wouldn't meet many of todays current standards but that's the way of development and learning.

When one engine was shut down to extend the cruise range, a stopped/feather propeller was no issue, but there were critical failure modes. To mitigate against oil pressure failure, which would allow the propeller to move under centrifugal force to the fully fine position, a flight fine pitch stop was introduced, activated when the undercarriage was retracted and deactivated when the undercarriage was extended. This ensured that constant speed was maintained throughout the approach thus allowing a rapid throttle response if required for a missed approach. The problem was that in the landing configuration, ie with the pitch stop withdrawn, if one engine failed or lost power the propeller would go the the fully fine position making in effect a solid disc next to the other propeller. If this sudden deceleration wasn't enough, the resultant disruption to the airflow over the tailplane gave a nose down pitch combining to make the aircraft irrecoverable without sufficient height - not usually available in a normal landing approach. Several Gannets losses were suspected to be due to this effect but without the aircraft being recovered they were not conclusive. However one that was lost on approach to RNAS Brawdy, and the wreckage was recovered with the position of the blades showing that this was almost certainly the cause.

[NutLoose]

PS853 has a Shack engine but has had the gearbox at the front modded with a firefly unit if memory serves me correctly, to convert it to a single prop, it also had other mods like part of the rear casing machined down and the lifting eyes on the rockers also cut down so it would fit, when doing engine changes etc they have to swop the rocker covers so they have the lifting eyes.

[oxenos]

On that you would feather both as if you could do only one the other would still be causing drag and trying to turn the engine…
On the Shackleton installation, the pitch control mechanism acted on the front prop. As the blades of the front prop moved, pinions mounted on the blade roots drove racks, which in turn moved a translation unit in a fore and aft direction. The translation unit was effectively a large bearing, one part of which rotated with the front prop, while the other rotated in the opposite direction with the rear prop. The fore and aft movement of the T.U. was transmitted by another lot of racks to pinions on the rear prop blades, so that they changed pitch (O.K. so far?)
The failure of a single rack could result in one of the six blades going fully fine. Trying to feather that prop resulted in five blades feathering with the sixth staying fully fine. Apparently this gave a slow rotation, some vibration, and some drag.
One one occasion we had a T.U. break up. There was some fire in the prop hub, where there was no extinguisher but that soon went out when all the bearing lubrication had burnt up. What was much worse was that when we tried to feather the prop, the front prop feathered but the rear went fully fine. Only about 300 R.P.M, no vibration, but an awful lot of drag. We were heavy, and were struggling with full power on the other three Griffons. Started the Vipers, but this was in the early days of the Viper installation when they could only run at full power or idle, and full power was limited to only a few minutes. (They later put in a continuous setting of around 95%)
Captain called for fuel jettison. Rather alarming, as the fuel jettison pipes were only a few feet from the Viper jet pipes, and Pilots Notes did not cover the subject. Got the weight down, and eventually landed safely.
Captain phoned Boscombe to ask why there was nothing in the notes about jettisoning fuel with the Vipers running. He was told that they had not tried it as it was considered too risky.

[ShyTorque]

I used to fly Bulldogs, powered by a single Lycoming with a CS prop.

On this type, the natural angle of the prop was fully coarse. After the engine started, engine oil pumped the CS unit into fine pitch, or as selected by the pilot. This meant that in the event of an engine failure the prop would feather itself.

The Achilles heel of the system was that the oil pump sat on the back of the engine, directly above the top of the nose oleo strut and very close to it. The significance of this was highlighted when a student pilot at RAF Cosford bounced the aircraft very hard on landing and porpoised a couple of times. The nose oleo was displaced upwards by his efforts and damaged the oil pump. The prop then moved into coarse pitch. Had the pilot stayed on the ground, no problem.

Unfortunately he decided to go around. The engine couldn’t produce much help with the prop in coarse pitch but supplied just enough power for the pilot to fly half a mile beyond the upwind end of the runway whereupon it gave up trying and dumped him unceremoniously into a field. Oops.

[MENELAUS]

I used to fly Bulldogs, powered by a single Lycoming with a CS prop.

On this type, the natural angle of the prop was fully coarse. After the engine started, engine oil pumped the CS unit into fine pitch, or as selected by the pilot. This meant that in the event of an engine failure the prop would feather itself.

The Achilles heel of the system was that the oil pump sat on the back of the engine, directly above the top of the nose oleo strut and very close to it. The significance of this was highlighted when a student pilot at RAF Cosford bounced the aircraft very hard on landing and porpoised a couple of times. The nose oleo was displaced upwards by his efforts and damaged the oil pump. The prop then moved into coarse pitch. Had the pilot stayed on the ground, no problem.

Unfortunately he decided to go around. The engine couldn’t produce much help with the prop in coarse pitch but supplied just enough power for the pilot to fly half a mile beyond the upwind end of the runway whereupon it gave up trying and dumped him unceremoniously into a field. Oops.

Commiserations. On having flown the bulldog.

[Jhieminga]

PS853 has a Shack engine but has had the gearbox at the front modded with a firefly unit if memory serves me correctly, to convert it to a single prop, it also had other mods like part of the rear casing machined down and the lifting eyes on the rockers also cut down so it would fit, when doing engine changes etc they have to swop the rocker covers so they have the lifting eyes.
There is an official Rolls-Royce modification to change the Griffon 58 from Shackleton configuration to fit in a Spitfire. The structural changes you mentioned are part of it but they also have to modify the carburettor settings to allow for a much lower idle rpm than the Shack ever used. I had the PDF that detailed the changes at one point but lost it somehow.

[meleagertoo]

Commiserations. On having flown the bulldog.
The sort of comment that is only ever seems to be made by people who never did.

[ShyTorque]

The sort of comment that is only ever seems to be made by people who never did.


Agreed. Like every aircraft, it has its failings, but I enjoyed my time flying and instructing on them.

[NutLoose]

There is an official Rolls-Royce modification to change the Griffon 58 from Shackleton configuration to fit in a Spitfire. The structural changes you mentioned are part of it but they also have to modify the carburettor settings to allow for a much lower idle rpm than the Shack ever used. I had the PDF that detailed the changes at one point but lost it somehow.

I have the full manual for it ;)

[Jhieminga]

Just curious, but does your manual include the numbers for that idle setting? IIRC the Shack used an idle around 1200 rpm while the original Spit Griffons were more in the 600-700 rpm range. The compromise was somewhere in between. I have always wondered why other Griffon types could handle the lower idle rpm but this one had to use a higher setting.