Actually, FlexibleResponse, the bleed duct from the APU to the number two engine is longer, as it must go forward, then aft to the number two engine.
Not on the L1011s I flew. I just dusted off a few manuals and…“The No 2 engine and the APU share
common ducting”.
The APU Load Compressor output joined this common duct after passing through the APU Isolation Valve situated very close to the APU compartment immediately below the No 2 Engine. This duct can also be isolated from the forward part of the pneumatic system by Aft Fuselage Isolation Valve.