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Controlling your aircraft, using the autopilot etc.

OverSpeed  

Postby jestepp65 » Wed Sep 13, 2017 1:10 am

What to do when the Bombardier CRJ-700 goes into overspeed on autopilot.
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Re: OverSpeed

Postby Octal450 » Wed Sep 13, 2017 3:04 am

It has no autothrottle, you must manage your speed by yourself.

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Re: OverSpeed

Postby jestepp65 » Wed Sep 13, 2017 4:05 am

Thanks :D
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Re: OverSpeed

Postby hamzaalloush » Wed Sep 13, 2017 6:07 am

My apologies if this is long winded, you can skip to the video for an example of how to fly the aircraft while maintaining speed,

You asked a broad question, in general it is basic flying skills, having the correct power setting, staying ahead of your aircraft and scanning your instruments regularly will help to avoid an over-speed situation,

but specifically for the CRJ-series since there is no auto-throttle, you can never fly 100% hands-off, setting the throttle position to the appropriate detent(CLIMB, TO/GA or MAX POWER), will command the FADEC and depending on the parameters you have set on your MCDU(such as reduced thrust) and your phase of flight, will let the aircraft to take care of your power requirements for you,

The correct thrust, Speed hold(IAS) and Vertical speed (VS) hold modes should be your main methods for controlling airspeed with pitch in vertical phases of flight, you use the power detents for anything but the cruise and landing phases, where you set the throttle by hand in the manual range.

I say should because the autopilot controller in this aircraft is a bit slow, and Speed hold(IAS) mode does not respond correctly for climb, so for now I'd simply use the Pitch mode for takeoff and climb until 10000 ft for example, i'll explain shortly.

In takeoff, you have your throttle set at the TO/GA detent, that is what your v-speeds on your PFD are calculated for by default, it is not good practice to firewall to Max Power for takeoff(although you could), the same could be achieved with a maximum thurst TO/GA, nor should you switch between thrust modes mid-roll(it's one or the other), as potentially you could risk having the incorrect reference to make a decision in a one-engine inoperative situation, once you have began your takeoff roll, make sure you don't have any configuration warnings or red alerts on your EICAS and continue scan of both of your EICAS and PFD instruments,

I'd rotate the aircraft just a bit after V1 and pull to whatever pitch that lets me maintain a speed at least V2+15, depending on how early and fast i pull and how heavy is my aircraft, for the CRJ700-family my aim for the pitch is going to be somewhere between 15-20 degrees, gears up shortly afterwards until acceleration height(that's 1000 ft agl), I'd level off at that height and set my power to CLB, accelerate and clean up my aircraft after VSI, until at least the VY speed, where i can continue climb in basic Pitch mode to 10000 ft at that speed.

This is in detail how i maintain speed for takeoff and climb with the current autopilot(Without Speed hold(IAS) mode), until 10000 ft:

- Set your flaps to 8*
- Pre-select your cruise altitude
- Press the FD button
- Move the throttle into the TO/GA detent (Press 'n' twice on your keyboard)
- Accelerate and pull the yoke just after V1, aim for a pitch of 15-20*, pulling fast enough to maintain a speed of at least V2+15kts after liftoff.
- You should raise the gear up shortly after liftoff.
- Maintain pitch and speed until you reach at least a height of 1000 ft
- Level off at that height
- Move the throttle back a step to the CLB detent (Press shift-n on your keyboard)
- Sync your attitude to the basic Pitch mode (Press ctrl-p on your keyboard)
- Enage autopilot in Pitch mode (Press ctrl-f on your keyboard)
- Accelerate until after VSI(~168kts) and clean up your aircraft
- Continue to accelerate at level altitude until at least VY(I'd like to aim for 230 kts)
- Finally use the vertical speed wheel to increase your pitch to whatever pitch that maintains a reasonable and safe climb speed below 250kts, until 10000 ft.

I made a video to show how I do this, with a timeline in the description for each step:
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Re: OverSpeed

Postby jestepp65 » Wed Sep 13, 2017 4:23 pm

Thank you so much for the answers :D
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