View Full Version : A note describing British auxiliary props

Bob Gardner
02-14-2018, 07:31 AM

This note also appears under Modern Wooden Propellers.

It would appear that all British auxiliary props were designed by the Royal Aircraft Factory, the RAF, which became the Royal Aircraft Establishment, RAE, after April 1918 to prevent confusion with the newly formed Royal Air Force.

In sequential order, the aux prop drg nos that I have recorded are:


T28141 two-bladed D18" 500w
T28142 two-bladed D24" 500W also marked PRA*6

T28150 two-bladed D18.5" 500W made by Betjeman
T28153 two-bladed D19.0" 500W marked for heating a pilot's flying suit

T28756A two-bladed D13.5" P33" (sic !) RCAF 10A/3445/AM


T29017 four-bladed D21" P14.2" Rotherham fuel pump
T29290 four-bladed dated April 1936
T29506 four-bladed D36" Martlet (......... Thus WW2) see below
Drg no nk four-bladed D42" RCAF

T29506 above was used on the British Martlet Target Tug. The Martlet was used by the British Royal Navy, initially as a ship-borne fighter. It was the Grumman F4F Wildcat. The RN called it a Martlet. This name derives from House Martlet, the old name for a House Martin and the Navy may have had in mind that the House Martin flew wonderfully but had minute legs and tiny feet; hence a small ungainly undercarriage.

About the best aviation sang-froid comment that I know of came from a navy flyer, towing a drogue over a RN destroyer for anti-aircraft practice. Tracer fire from the ship passed just in front of the Martlet. The pilot radio-ed to the ship, I am towing this target, not pushing it!

02-28-2018, 09:46 AM
Thank you for such a well explained and researched post.

I thought there may interest in some other examples of 2 bladed auxiliary props with drawing numbers of:

T28152 - which is also stamped "Short Bros 184 160 HP" on the hub;

T29981/2 stamped with AM and crown;

an example of the T128142 but stamped Oddy; and

a metal example T29091 dated 1936 again with the AM and Crown.

I'd be grateful to hear any additional information about these examples.


Bob Gardner
05-06-2018, 08:32 AM
Thank you Paul,

I have added your data to my spreadsheet.

For new forumites, the letter T on these numbers indicates the Royal Aircraft Factory (RAF) which became the Royal Aircraft Establishment (RAE) on the formation of the Royal Air Force on 1st April 1918.

This thread refers to small auxiliary propellers mostly about eighteen inches in diameter mounted in the slip stream of the aircraft to provide power for pumping fuel and for generating electricity. During WW1 these were mounted on a wing strut.

The concept is still in use to this day. Modern large aircraft have a propeller attached to a generator which can generate electricity or hydraulic pressure. It is called a ram air turbine (RAT) and is lowered from the fuselage into the airflow in emergency. Google tells me that in some military aircraft, such as the Saab 37 Viggen, the RAT is used during takeoff and landing for the pilot to be able to manoeuver the plane in case of an engine failure at low altitude.

T28152 was a nineteen inch wooden aux prop mounted on aircraft such as the Vickers Vimy to generate electricity: 500 Watts.

T28153 was probably the same design but one example I have seen had a note 'for heating a pilot's suit.' This in 1918!

T128142 listed by Paul is an anomaly because Paul, or much more likely the man who stamped the data on the prop, mis-typed T28142. Stamping errors of data on wooden props was comparatively frequent in WW1 when data were repetitively hand stamped.

Smaller aux props in the airstream were mounted direct to a fuel pump (a Rotherham Pump) which pumped fuel from the main tank to the gravity tank mounted in the upper wing.

With kind regards,