SE5a propellers

[jaw]

At Tangmere Military Aviation Museum we have an SE5a replica of the cockpit area, but it has an original 4 bladed propeller - which is marked SE5a and Hispano- Suiza 200hp. Yet I have seen pictures and references to the SE5a which show it with a 2 bladed propeller. So my question is why did some SE5a's have 4 bladed propellers and why did some have 2 bladed propellers?

 

Thanks,

 

John

 

 

[Corsairfoxfouruncle]

Good question, i was just researching that myself for a future build.

[malpaso]

Well there's geared and ungeared Hispano Suizas, and then the Wolseley "copy", each of these would have slightly different characteristics so need different propellers.  Props on geared vs non geared may even rotate in opposite directions?

[Graham Boak]

I suspect this is the difference between geared and ungeared engines, but don't know that for sure.  It does seem likely that some such difference would be required.

Edited August 14, 2019 by Graham Boak

[Smithy]

On 8/14/2019 at 8:23 PM, jaw said:

At Tangmere Military Aviation Museum we have an SE5a replica of the cockpit area, but it has an original 4 bladed propeller - which is marked SE5a and Hispano- Suiza 200hp. Yet I have seen pictures and references to the SE5a which show it with a 2 bladed propeller. So my question is why did some SE5a's have 4 bladed propellers and why did some have 2 bladed propellers?

 

Thanks,

 

John

 

 

 

Sorry John for the late reply as I missed this.

 

The two bladed propeller was used with all various SE5 and SE5a engines. The four bladed propeller was only used on the geared 200hp Hispano Suiza engine with the first installation of it on the third prototype, A4563.

 

Source: Sturtivant & Page, "The S.E.5 File"

 

HTH,

 

Tim

[jaw]

Thanks Tim - another mystery solved via BM!

 

John

[John Aero]

Direct drive, high revving  propellers tend to be small and finer pitched.  As engine power increases and with gearing introduced to keep the revs within limits, the extra power needs to be absorbed by a larger prop, but an increase in diameter may not be possible due to airframe and under-carriage design. By retaining the same diameter but increasing the number of blades was a practical solution initially for fixed pitch propellers. Just look at the Spitfire family, two blades to six, even with variable pitch props.

 

A simple solution to a larger prop might appear to be an increase of the under-carriage length, but this can have an adverse effect, for instance by changing the ground angle and therefore the take off characteristics due to the wing assuming a greater incidence due to the ground angle.

 

John

[jaw]

Thanks John - that answers the question.

 

John