Probably a good idea
Some additional information about irl engine start for anyone interested:
Jet Engine Start (except 787)
The APU is a small, NiCad battery started engine located in the tail. The APU produces bleed air (pneumatic) which is required for engine start and other pneumatic systems. The APU also drives a generator for electricity production.
In-flight power is produced by engine driven generators. If an engine or generator fails, the APU is restarted to bring a second generator online.
If an APU is not functional, a ground air cart is then used for engine start. Engine start requires pressurized air in the 30 - 42 PSI range, depending on engine.
Note: a working APU is required for ETOPS (extended operations), but flights over populated land areas (ie lower 48 US) are allowed with an inop APU as repair can be deferred under MEL.
Once one engine is started, the second engine can be started with cross bleed from the running engine.
The Boeing 787
787 has two high power Li Ion batteries (opposed to the NiCad on other jets). The Li Ion battery is used for engine start.
There are no pneumatic systems on the 787, all 787 systems are high power electric including pressurization. The engines do produce bleed air, but use is limited to engine cowl anti-ice & hydraulic pressurization.
You are correct in that the 787 does have an APU - the 787 APU is for backup electricity production (system redundancy).
This is a brief summary about irl engine start and the APUs for those interested. If anyone has questions about irl aircraft systems, fire away, I’m happy to answer any irl questions.