(Pre-)Engine Start and APU questions
I have two little questions about the pre start procedures in the Q400 that may or may not have somewhat obvious answers but I haven't found them yet.
1) Most operators limit use of the APU to certain OAT ranges that can be fairly restrictive. As I see no other way to air condition the cabin before the engines are running, does this mean that you will regularily board an aircraft that is cold as all hell in winter? Cabin's showing 10-15°C when boarding at the moment and the only available heat source is the APU, right? Is it common to operate the APU during boarding to heat up the cabin or is this typically a no-no? If so, do you sit down in a ten degree cabin when you board a Q400 or is there another way to A/C it that I'm not aware of?
2) If you cannot start up your engines on the stand while still connected to GPU, because a startup during or after pushback is mandated by the aircraft or airport operator, you'd run the APU to facilitate power for engine start, correct? Since operation of the APU is quite restricted on this particular aircraft I'm honestly not sure here. Say it's 22°C outside and you have to start them up during the push - do you run the APU here or throw it on the batteries? I've been avoiding battery starts like the plague, am I right to do so or are they actually more common with the Q400 due to the restrictive APU procs?
Comments
There is a ground air conditioning connection for the external supply of the aircraft's flight deck and cabin with warm or cold air.
As a rule, since the Dash is almost exclusively in outdoor areas, an engine can be started there as long as the GPU is still connected. If not, there are clear rules for starting with APU.
Such special features should certainly be discussed in advance with the airlines and the airport operator.
Thanks for the input. So since ground bleed air is not modelled, we're left with a little make-believe here that we heated her up for the PAX, that's okay, just wanted to confirm.
And I guess it makes sense what you say about startup and the APU. My regular procedure when pushback is required is to start No. 2 on ground power, unfeather, then start No. 1 during the pushback (when the ground crew clears you to start No. 2 actually) or on the taxiway after completion of push when everybody is confirmed clear, making use of the No. 2 generator. This seems quite feasible from an engineering point of view but a little sketchy from a ground safety perspective to start and unfeather a prop while still at the gate. It's also kind of unusual and means you gotta ignore Majestic's ground crew when they tell you when to start them up, but it's a common procedure in the real world, I take it? That's pretty much what I'm reading into your reply and it also just makes sense.
From minutes 12-16 you can see the variant that I prefer and that I know so many times
In my experience operating the Dash 8 in real life (only series 200/300, no 400), yes we would regularly board the airplane with temperatures in uncomfortable ranges. If you put your foot down and demanded an air cart or to run an engine to get conditioned air flowing in the name of passenger comfort that usually did the trick. Some Captains would just accept the uncomfortable temps, when I upgraded I decided I would never be uncomfortable so I didn't stand for it.
When we didn't have an APU available (200 series didn't have them installed, 300 series often had them INOP) we would do a GPU start - only DC... I never used an AC GPU, I believe that's primarily for MX.
In a GPU start, make sure the batteries are all on, the Main Bus Tie is On, then start both engines leaving them in Start&Feather. Disconnect from External Power, complete your pushback and upon release from guidance, condition levers go to max and complete your before taxi flows.
In our 300 series airplanes that had APUs installed, when they worked, we would typically start one engine off a GPU leaving it in Start&Feather, start the pushback and start the other engine on the push with the assistance of the #2 DC GEN and the APU GEN. We never pushed back with the engines in anything but start&feather for ground crew safety, as well has keeping it easy on the tug. A Dash engine in MAX generates significant thrust and prop blast, so by pushing back with the engine in MAX you're having the tug work extra hard.
You're correct that battery starts are to be avoided if at all possible. They're do-able but you're rolling the dice with a hot start or a hung start, plus you better have some manual load shedding techniques up your sleeve to get some more oompf out of the batteries. They're just not strong enough.
Hopefully that sheds some light on some real world SOP.
Really good stuff, thank you very much for the explanations. Great to get that kind of insight and I'll incorporate that into my procedures. Many thanks all around.