The photos are basically sorted out and uploaded to flickr. Feel free to visit. Today I’m writing about a niche topic: the APU of the BAE Systems Hawk trainer.

This time, watching the spectacular aerobatic formation flying of the British RAF Red Arrows at Zhuhai, they use the Hawk trainer manufactured by British BAE Systems.

Looking closely at the details in the photo below, you can see several holes on the upper fuselage, it’s natural to assume these are the intake and exhaust vents for the Auxiliary Power Unit (APU). (The rectangular one at the front is the intake, the black circular one at the back is the exhaust.)

I looked up some information online and found that the Hawk trainer likely uses the Saphir 10 Auxiliary Power Units (APU), produced by Safran Power Units, a subsidiary of the French Safran S.A.

In the product description, you can see the location of the APU in the airframe, which matches the photo taken in Zhuhai above.

The technical data for this APU is as follows: Length 25 inches 63.5 cm Width 12 inches 30.5 cm Height 13 inches 33 cm Net Weight 81 lbs 36.7 kg

Ground Start Altitude 0 to 22,640 ft Temperature -78.8 to 122 °F In-flight Start Altitude 0 to 35,100 ft Temperature -104 to 122 °F

Mechanical Power 69 kW Electrical Power 12 kVA

The Saphir 10 APU needs to work with the ATS-323 Air Turbine Starter, which is also produced by Safran Power Units. The product description also shows an illustration of its location inside the airframe: Its dimensions are smaller, with a length of 9.5 inches (24 cm), width of 7.9 inches (20 cm), height of 7.9 inches, and a weight of only 15.5 lbs, which is 7 kg.

By the way, do the Su-27 and J-10 not have APUs? I took so many photos and looked for a long time but couldn’t see any APU intake or exhaust holes, so I guess they don’t have them. To save weight and install more important equipment instead of an APU, besides, there are always ground power units on the tarmac. (The Mig29 seems to have one)

Incidentally, regarding Russian APUs and engine starters: Krasny Octiabr AUXILIARY POWER UNIT VSU-117 85Kg Klimov GTDE-117 gas-turbine engine (turbine starter) 42Kg They are much heavier than the one used in the Hawk.