Heavy oil (diesel) engines were specified by the Air Ministry because the airship was intended for use on the India route, where it was thought that high temperatures would make petrol an unacceptable fire hazard because of its low flash point.
 A petrol explosion had been a major cause of fatalities in the loss of the R.38 in 1921.

Initial calculations were based on the use of seven Beardmore Typhoon six-cylinder heavy-oil engines which were expected to weigh 2,200 lb (1,000 kg) and deliver 600 bhp (450 kW) each.
When the development of this engine proved impractical, the use of the eight-cylinder Beardmore Tornado was proposed instead.
This was an engine being developed by Beardmore, combining two four-cylinder engines which had originally been developed for railway use.
 In March 1925 these were expected to weigh 3,200 pounds (1,500 kg) and deliver 700 bhp (520 kW) each.
Because of the increased weight of each engine, it was decided to use five, resulting in overall power being reduced from 4,200 bhp (3,100 kW) to 3,500 bhp (2,600 kW).

Severe torsional resonance of the crankshaft was encountered above 950 rpm, limiting the engine to a maximum of 935 rpm, giving an output of only 650 bhp (485 kW) with a continuous power rating at 890 rpm of 585 bhp (436 kW).
 The engine was also considerably above estimated weight, at 4,773 lb (2,165 kg), over double the initial estimate.
Some of this excess weight was the result of the failure to manufacture a satisfactory lightweight aluminium crankcase.

The original intention had been to fit two of the engines with variable-pitch propellers in order to provide reverse thrust for manoeuvring during docking.
The torsional resonance also caused the hollow metal blades of these reversing propellers to develop cracks near the hubs, and as a short term measure one of the engines was fitted with a fixed-pitch reverse propeller, consequently becoming dead weight under normal flight conditions.
 For the airship's final flight, two of the engines were adapted to be capable of running in reverse by a simple modification of the camshaft.

Each engine car also contained a 40 bhp (30 kW) Ricardo petrol engine for use as a starter motor.
 Three of these also drove generators to provide electricity when the airship was at rest or flying at low speeds: at normal flight speeds the generators were driven by constant-speed variable-pitch windmills.
The other two auxiliary engines drove compressors for the compressed air fuel and ballast transfer system.
 Before the final flight, one of the petrol engines was replaced by a Beverly heavy oil engine; to lessen the risk of fire, the petrol tanks could be jettisoned.

Diesel fuel was contained in tanks in the transverse frames, the majority of the tanks having a capacity of 224 imp gal (1,018 l).
A mechanism was provided for dumping fuel directly from the tanks in an emergency.
By the use of tankage provided for weight compensation, when travelling with a light passenger load a total fuel load of 10,000 imp gal (45,000 l) could be carried.
Heavy oil (diesel) engines were specified by the Air Ministry because the airship was intended for use on the India route, where it was thought that high temperatures would make petrol an unacceptable fire hazard because of its low flash point.  A petrol explosion had been a major cause of fatalities in the loss of the R.38 in 1921.
Initial calculations were based on the use of seven Beardmore Typhoon six-cylinder heavy-oil engines which were expected to weigh 2,200 lb (1,000 kg) and deliver 600 bhp (450 kW) each. When the development of this engine proved impractical, the use of the eight-cylinder Beardmore Tornado was proposed instead. This was an engine being developed by Beardmore, combining two four-cylinder engines which had originally been developed for railway use.  In March 1925 these were expected to weigh 3,200 pounds (1,500 kg) and deliver 700 bhp (520 kW) each. Because of the increased weight of each engine, it was decided to use five, resulting in overall power being reduced from 4,200 bhp (3,100 kW) to 3,500 bhp (2,600 kW).
Severe torsional resonance of the crankshaft was encountered above 950 rpm, limiting the engine to a maximum of 935 rpm, giving an output of only 650 bhp (485 kW) with a continuous power rating at 890 rpm of 585 bhp (436 kW).  The engine was also considerably above estimated weight, at 4,773 lb (2,165 kg), over double the initial estimate. Some of this excess weight was the result of the failure to manufacture a satisfactory lightweight aluminium crankcase.
The original intention had been to fit two of the engines with variable-pitch propellers in order to provide reverse thrust for manoeuvring during docking. The torsional resonance also caused the hollow metal blades of these reversing propellers to develop cracks near the hubs, and as a short term measure one of the engines was fitted with a fixed-pitch reverse propeller, consequently becoming dead weight under normal flight conditions.  For the airship's final flight, two of the engines were adapted to be capable of running in reverse by a simple modification of the camshaft.
Each engine car also contained a 40 bhp (30 kW) Ricardo petrol engine for use as a starter motor.  Three of these also drove generators to provide electricity when the airship was at rest or flying at low speeds: at normal flight speeds the generators were driven by constant-speed variable-pitch windmills. The other two auxiliary engines drove compressors for the compressed air fuel and ballast transfer system.  Before the final flight, one of the petrol engines was replaced by a Beverly heavy oil engine; to lessen the risk of fire, the petrol tanks could be jettisoned.
Diesel fuel was contained in tanks in the transverse frames, the majority of the tanks having a capacity of 224 imp gal (1,018 l). A mechanism was provided for dumping fuel directly from the tanks in an emergency. By the use of tankage provided for weight compensation, when travelling with a light passenger load a total fuel load of 10,000 imp gal (45,000 l) could be carried.
R101