Quick Startup/Operations questions for Bizjet / Commuter liner pilots

[PeetPeet]

Hello,

I'm new to the forum - not a professional pilot, just a PPL holder.
I'm actually an aerospace design engineer researching for a new aircraft design, I thought this would be a good place to ask a couple of operational questions of the product end-user and that's you, the pilot(s).

Thank you in advance for your answers, no exceptional detail or accuracy is required, but it would help me out a lot if any corporate business jet pilots or commuter-liner pilots, such as Citation X, Hawker 4000, Gulfstream, CRJ, Embraer ERJ-145 etc could try to answer the following;

-On a twin engined aircraft, what is the duration of time elapsed between beginning the start sequence of the number 1 engine to the time the number 2 engine is running?
Purpose of this question is to figure out how long the PTU might run on startup.

-Furthermore, how long would an airplane typically sit with just one engine running when waiting for passengers perhaps? An average time and frequency would be great - again, trying to hone in on PTU operation time.

-During recurrent training, how long on a typical training flight might you practice single engine ops with one engine throttle retarded? How frequent are such training flights?

-Lastly, during a startup check list sequence, how long would you run the EMP (auxiliary electric motor pump) for to test its operation? Is it a quick on-off, just a few seconds? Or longer?

Your time and answers are much appreciated - I can't tell you what I'm working on, but some of you will one day be flying it, this is your chance to help with the development of a new airplane! :)

Thanks,

-Pete

[Mach E Avelli]

There are too many variables to give you an accurate answer. Depends whether ground power or APU is used to assist the start, or whether the start initialises from ship's batteries, and is very type-specific.
For example, B737 with APU, the time between starts could be less than a a minute and no PTU will run in this time.
Something like a Metro or King Air starting on ship's batteries, could require one engine to run for several minutes to put enough charge back in and reduce generator load before starting second engine.
Something like a small Citation (no APU), the pilots may elect to start one engine and run it 20 minutes or so while they do cockpit setup checks - because the batteries alone could not cope with the load for that time.
An ATR 42 would have number 2 engine running continuously on every turnaround as it acts as the APU and provides power and air-conditioning.
None of the above aircraft will have a PTU running during this process (some don't even have a PTU), but other types may.
As for pumps - hydraulics may be powered electrically on some types (e.g. B737) at all times in the pre-start process until engine driven pumps pick up the load, so could be running on all turnarounds. Electric fuel pumps ditto -again depends on type and individual company policy. Some pumps are run continuously or have an auto function so that they cut in whenever not supported by engine-driven pumps.

[galaxy flyer]

Bizjets, with APUs pretty much run on the APU until pax arrive and then it is about 4 minutes to start and taxi. Time on one-engine would be less than a minute. APUs are pretty common now.

Recurrent training is all done in the sim, so not a factor for the plane. Probably have a hard time cert'ing a FAR 25 without a sim today.

Any ground checks are pretty momentary, on the Global, the longest check (stall protection) is about 15-20 seconds, the shortest, blink and you'll miss it.

GF