How to hold airspeed during cruise.

[Matthew Tunkelo-Bonner 0]

I have worked out how to hold the airspeed during climb.

But as soon as it gets to cruise it always disconnects and I have to set the throttle manually, same on descent and landing. After climb the speed button does not want to engage.

How do you work around this?

[Dornus 1]

The aircraft didn't have a Autothrust. You have to adjust thrust manually during cuise.

So you have a look on the speed all the time and if needed you have to adjust thrust manually.

 

 

[Thx1137 65]

To explain more. Speed mode uses pitch to control the speed, it can't do that when flying level.

[JRBarrett 675]

In the real CRJ the pilot has to manually control thrust in cruise to hold the desired airspeed. In my experience, at altitudes above FL300, an N1 setting of around 81.5 percent will give about Mach 0.77

 

If you are not using Live Weather the temperature, wind and pressure at cruise altitude will never change, and once you find an engine N1 setting that gives you a desired cruise speed, you can often cruise for many minutes without ever touching the throttles. With Live Weather active, you will have to adjust thrust more often.

 

In automotive terms, the CRJ has no “cruise control”. Unlike more advanced aircraft with autothrottles, in the CRJ, you cannot walk away when in cruise and do something else, depending on the automatic systems to manage your speed. You need to stay in the cockpit throughout the entire flight to manage your speed manually.

 

On the airspeed display , right next to the pointer showing your current airspeed, there will be a magenta-colored trend vector, which is a vertical line that points above or below the current airspeed that shows if your current airspeed is increasing or decreasing. Your goal should be to adjust engine thrust to shrink the trend vector so it disappears. If the trend vector shows your airspeed is increasing, reduce thrust a little, or if decreasing, increase it a little.

[Claviateur 4]

I have no knowledge of engineering or aircraft design, but I am puzzled that an aircraft of this generation does not have this automation.

 

There is a reason perhaps behind this design choice from Bombardier.

 

In fact the whole automation seems a little quirky to me. 

[JRBarrett 675]

It is actually typical for the CRJ design period (early 1990s). The competing Embraer EMB145 and 135 regional jets from the same period have no autothrottles either. Both the CRJ and Embraer are designed for relatively short legs of one or two hours. Other aircraft from that era, such as the 737/747/757/767 are designed for long distance flights, where autothrottles and full coupled VNAV would be more useful to relive pilot workload.

 

Both the CRJ 700/900 and the EMB 135/145 have FADEC controlled engines with fixed thrust detents for takeoff and climb and a variable range for cruise and descent. An autothrottle is not compatible with that kind of system.

 

Autothrottles actually are available as an aftermarket add-on for the older CRJ-200. That is possible because the  CRJ-200 does not have FADEC, or fixed throttle detents - the power levers are simple continuously variable controls that go from idle to max thrust.