Internal Starting on the Dash 8
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Internal Starting on the Dash 8
In the flight manual it states that the first engine that is started has to be operated out of feather, prior to starting the second one. (100/300)
My question is why ? What advantage is gained by unfeathering the propeller ?
My question is why ? What advantage is gained by unfeathering the propeller ?
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Originally Posted by Capt. Greaseon
In the flight manual it states that the first engine that is started has to be operated out of feather, prior to starting the second one. (100/300)
My question is why ? What advantage is gained by unfeathering the propeller ?
My question is why ? What advantage is gained by unfeathering the propeller ?
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On those hot days, you can never get cold air blasting through the plane soon enough. So unfeathering it would get more air coming your way.
You dont have to unfeather the first one prior to starting the second one.
Our manual stated to keep them both in feather until the tow bar and/or external power is disconnected.
Must be a company specific thing for you guys, kinda like our rule of having to use flaps 15/yaw damper off in our 300's on certain short runways or intersection takeoffs.
You dont have to unfeather the first one prior to starting the second one.
Our manual stated to keep them both in feather until the tow bar and/or external power is disconnected.
Must be a company specific thing for you guys, kinda like our rule of having to use flaps 15/yaw damper off in our 300's on certain short runways or intersection takeoffs.
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Originally Posted by doglegfinal
why would you have yaw damper off then ?
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Originally Posted by DHC8-FO
You dont have to unfeather the first one prior to starting the second one.
Our manual stated to keep them both in feather until the tow bar and/or external power is disconnected.
Our manual stated to keep them both in feather until the tow bar and/or external power is disconnected.
The Flight Manual states:"When battery starting, unfeather propellor of first engine and delay start of second engine for 30 secs to allow completion of flight guidance computer start-up self-test."
In our company, we do battery starts with the bus feed CB's pulled, bus tie off and inverters off. After starting #2, unfeather and then reset CB's, inverters on and tie buses.
When the prop is unfeathered, the AC gen comes online. I can only imagine that that is the reason, to make an extra generator available. With APU starts, you have the APU gennie helping and with external you don't need generated power (in fact DC gennies are isolated while external power selected).
Hope this helps Capt Grease-on.
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Originally Posted by DHC8-FO
Must be a company specific thing for you guys, kinda like our rule of having to use flaps 15/yaw damper off in our 300's on certain short runways or intersection takeoffs.
Please post if you find it. I am quite interested as well.
We fly the Model 315 and always take-off with yaw damper, in fact mandated by AFM.
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Thanks nugpot
Ok here is a scenario for you. You have started the #2 engine with a GPU and then the GPU is removed. You now have just the #2 DC GEN available. Now are you required to unfeather before starting the #1 engine ?
What I am getting at is that unfeathering the propeller will bring the #2 AC GEN online and via the TRUs will power the secondary DC buses. However neither of these will influence the start of the #1 Engine.(#1 Starter would be powered from left main DC bus)
Just wondering if there was any electrical advantage gained in by the prop operating out of feather, that would be beneficial when trying to start, the opposite engine ?
Ok here is a scenario for you. You have started the #2 engine with a GPU and then the GPU is removed. You now have just the #2 DC GEN available. Now are you required to unfeather before starting the #1 engine ?
What I am getting at is that unfeathering the propeller will bring the #2 AC GEN online and via the TRUs will power the secondary DC buses. However neither of these will influence the start of the #1 Engine.(#1 Starter would be powered from left main DC bus)
Just wondering if there was any electrical advantage gained in by the prop operating out of feather, that would be beneficial when trying to start, the opposite engine ?
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The AFM (as I mentioned earlier) specifically refers to the start-up test of the flight guidance computer. It might be possible that this (powered from the secondary feed bus) needs power and that bus is now not powered (it would be powered with either APU gen or Ext power online).
Another possibility is that by having the bus tie closed (as you would have for normal starting) without APU or Ext DC power, simulates double TRU failure with both DC gennies operating - and that would cause main-secondary ties to close. Now you have one 300A generator powering ALL buses AND still recharging a battery that just took a 1200A hit.
Sorry, I can just give you my best guess. We either start both on GPU/APU or follow the full battery start procedure.
Another possibility is that by having the bus tie closed (as you would have for normal starting) without APU or Ext DC power, simulates double TRU failure with both DC gennies operating - and that would cause main-secondary ties to close. Now you have one 300A generator powering ALL buses AND still recharging a battery that just took a 1200A hit.
Sorry, I can just give you my best guess. We either start both on GPU/APU or follow the full battery start procedure.
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What Capt. Greaseon says is correct
So much so that on the rare occasions I have done a BAT/Internal start I have not taken #2 Eng out of feather. Electrically it make no sense to do so.
Also the other reason I will not unfeather the prop is that if a push back is then required you would end up being pushed with props unfeathered
So much so that on the rare occasions I have done a BAT/Internal start I have not taken #2 Eng out of feather. Electrically it make no sense to do so.
Also the other reason I will not unfeather the prop is that if a push back is then required you would end up being pushed with props unfeathered
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DV8 that is what I'm trying to find out why that procedure is in the Flight manual.
I'm actually off to the sim in a few days, and as luck has it we do our sim training right next door to Bombardier, maybe I might be able to get an answer while I'm there.
I'll let u guys know if I do.
I'm actually off to the sim in a few days, and as luck has it we do our sim training right next door to Bombardier, maybe I might be able to get an answer while I'm there.
I'll let u guys know if I do.
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The reason to unfeather the prop after starting the first engine according to me is not the extra electrical power you get for starting the second engine but to help in charging your battery before starting your second engine.
It indeed states in the AFM:
"When battery starting, unfeather propellor of first engine and delay start of second engine for 30 secs to allow completion of flight guidance computer start-up self-test."
But in my book it also states to: "delay an engine start until the main battery load is below +.50."
So to get the battery load below .50 engage your AC generator by unfeathering your propeller.
About push back with both engines unfeathered.
We used to do that but not anymore. The reason is that if your P/L is not at or aft of disk your nose gear will be subjected to undue stresses.
It indeed states in the AFM:
"When battery starting, unfeather propellor of first engine and delay start of second engine for 30 secs to allow completion of flight guidance computer start-up self-test."
But in my book it also states to: "delay an engine start until the main battery load is below +.50."
So to get the battery load below .50 engage your AC generator by unfeathering your propeller.
About push back with both engines unfeathered.
We used to do that but not anymore. The reason is that if your P/L is not at or aft of disk your nose gear will be subjected to undue stresses.
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Originally Posted by D-OCHO
About push back with both engines unfeathered.
We used to do that but not anymore. The reason is that if your P/L is not at or aft of disk your nose gear will be subjected to undue stresses.
We used to do that but not anymore. The reason is that if your P/L is not at or aft of disk your nose gear will be subjected to undue stresses.
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Yea be careful on those pushbacks. We do them pretty much all of the time at the larger airports where they park you into an alley with other dashes and RJ's wingtip to wingtip.
The other week we were doing a pushback, and the rampers, after connecting the tow bar to the airplane correctly, neglected to connect the tug to the towbar, just rested it up against it i suppose (no pin). Anyrate, he started pushing us, made a very wide turn and slowed down and/or hit the brakes, and the tug stopped and we just kept on rolling back with the towbar connected, no engines started yet. The tow bar and nose gear ended up doing a full 360 turn beneath us, made an awful sound. Needless to say that plane sat there for a while right in the top of the alley while we deplaned the pax, etc. Shame. It isnt required that we have headset comm. with the drivers, and they didnt this night.
And it was the last leg back home on the end of a 4-day trip, why does s*** always break on the last leg home????????
The other week we were doing a pushback, and the rampers, after connecting the tow bar to the airplane correctly, neglected to connect the tug to the towbar, just rested it up against it i suppose (no pin). Anyrate, he started pushing us, made a very wide turn and slowed down and/or hit the brakes, and the tug stopped and we just kept on rolling back with the towbar connected, no engines started yet. The tow bar and nose gear ended up doing a full 360 turn beneath us, made an awful sound. Needless to say that plane sat there for a while right in the top of the alley while we deplaned the pax, etc. Shame. It isnt required that we have headset comm. with the drivers, and they didnt this night.
And it was the last leg back home on the end of a 4-day trip, why does s*** always break on the last leg home????????
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I haven't flown a DH8 for about 6 years but a vague recollection says that after the first ship's battery start, the charge rate on the battery must be below a certain value before the second engine start is commenced.
Bringing the prop out of feather brings the AC generator on-line. I think having the AC gen on-line allows more of the output of the DC gen to recharge the batteries, whilst the AC gen powers the rest of the ship's services.
Bringing the prop out of feather brings the AC generator on-line. I think having the AC gen on-line allows more of the output of the DC gen to recharge the batteries, whilst the AC gen powers the rest of the ship's services.
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Originally Posted by Capt Claret
I haven't flown a DH8 for about 6 years but a vague recollection says that after the first ship's battery start, the charge rate on the battery must be below a certain value before the second engine start is commenced.
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With just the batteries on you have the Main buses as well as the essential buses powered. After you start the first engine you have the and leave it in feather you still only have the mains and essentials powered.(The difference is 28 volts from the DC GEN instead of 24 volts from the bat)
Bringing the propeller out of feather now activates the AC GEN for that engine. It will now power the secondary buses via the TRUs. The DC GEN is still powering mains and the essentials. You now have the whole dc system available, however the load on the DC GEN has not changed because it is still powering the same buses it was before you unfeathered the propeller.
Off to sim today I'll see u guys in a couple of days.
Bringing the propeller out of feather now activates the AC GEN for that engine. It will now power the secondary buses via the TRUs. The DC GEN is still powering mains and the essentials. You now have the whole dc system available, however the load on the DC GEN has not changed because it is still powering the same buses it was before you unfeathered the propeller.
Off to sim today I'll see u guys in a couple of days.
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Sorry for no reply guys, had lousy sim times. Try 3.00 am and 1.00am, and obviously no one around at that time. Still trying to source the answer as soon as I find anything I will let you know.
