Jump to content

Anti ice and engine thrust?


janjoensson
 Share

Recommended Posts

Hi!

 

This is a question strictly out of interest, not a support issue. 

When on ground taxing the CRJ 700, with wing anti-ice turned off, you need a little bit of throttle power to start moving. However, when turning the wing anti-ice on, the engines spool up a bit and the CRJ moves on idle. Is that how the aircraft behaves also in real life? I think it is very handy, but would be interesting to know if anyone knows why and if this happens also in the real plane. 

 

Best regards

 

Jan

Link to comment
Share on other sites

6 minutes ago, Hans Hartmann said:

Yes. Anti-ice systems need bleed air, and to produce more bleed air, the idle N1 is increased. For cowl anti-ice only, it's to about 30% and for cowl and wing anti-ice it's 35%.

Thank you very much for this informativa answer! Is it normal to taxi with wing and cowl anti-ice on, or is it normally turned on in a later stage during flight?

Link to comment
Share on other sites

  • CRJ Forum Moderator
19 hours ago, janjoensson said:

Thank you very much for this informativa answer! Is it normal to taxi with wing and cowl anti-ice on, or is it normally turned on in a later stage during flight?

Using cowl anti ice during taxi would be standard practice any time the outside air temperature is below 10C and visible moisture exists (rain snow or fog). I’m not sure about the use of wing anti ice on the ground in the 700/900 series. I work (in maintenance) on CRJ200s, and the maintenance manual cautions that when testing the wing anti ice on the ground, to leave it enabled only long enough to do the required tests and then turn it off,  otherwise the leading edges could overheat and become damaged. The 700/900 may be different. This would be a question for one of the r/w pilots on the test team.

 

That said, our 200s are equipped with an optional “low temperature wing anti-ice system” that can be used for an unlimited amount of time on the ground. This system supplies bleed air at reduced pressure and flow rate (with temperature regulation) providing sufficient heating to prevent freezing precipitation from accumulating on the leading edges but not enough to potentially damage the leading edges from overheating. The LTWAIS may be unique to the 200. Because that model has no slats, it is far more likely to experience degraded lift on takeoff if there is any leading edge contamination.

  • Like 2
  • Thanks 1
  • Upvote 1
Link to comment
Share on other sites

2 minutes ago, JRBarrett said:

Using cowl anti ice during taxi would be standard practice any time the outside air temperature is below 10C and visible moisture exists (rain snow or fog). I’m not sure about the use of wing anti ice on the ground in the 700/900 series. I work (in maintenance) on CRJ200s, and the maintenance manual cautions that when testing the wing anti ice on the ground, to leave it enabled only long enough to do the required tests and then turn it off,  otherwise the leading edges could overheat and become damaged. The 700/900 may be different. This would be a question for one of the r/w pilots on the test team.

 

That said, our 200s are equipped with an optional “low temperature wing anti-ice system” that can be used for an unlimited amount of time on the ground. This system supplies bleed air at reduced pressure and flow rate (with temperature regulation) providing sufficient heating to prevent freezing precipitation from accumulating on the leading edges but not enough to potentially damage the leading edges from overheating. The LTWAIS may be unique to the 200. Because that model has no slats, it is far more likely to experience degraded lift on takeoff if there is any leading edge contamination.

Thank you very much! Very interesting information 😁

  • Like 1
Link to comment
Share on other sites

Ok, I 'd like to chime in here. This is one of the cases where the AS CRJ does not behave like the real aircraft. As you can see in the first video of a CRJ 900 (in this regard not different to the CRJ 700), which was recorded before takeoff, there is no increase in engine RPM on ground - not even with both WING and COWL A/I ON. There is a slight rise in ITT, but the RPM remains in (after landing: reverts to) ground idle, which on some aircraft can trigger a L/R WING A/I caution message, indicating an underheat condition. This is acceptable on ground since WING A/I is switched ON not until line-up clearance and switched OFF shortly after leaving the runway. BTW: In the video you can also see, that the use of anti-ice always cancels a previously entered FLEX thrust, which does not happen on the AS CRJ.

 

Anti-ice in flight is a different story. The second video shows what happens when WING and COWL A/I is switched ON in idle descent. While COWL A/I alone has almost no (if any) effect on performance, the use of WING A/I causes FADEC to raise the engine idle RPM automatically to ensure that the airpressure in the pneumatic duct is sufficient for effective wing anti-icing. This results in a considerable increase of engine thrust, that must be taken into account for descent planning. During climb it's the other way around: Using WING A/I causes a significant loss in climb performance, which can negatively affect the ability to meet altitude restrictions etc. That's why it is permissible to switch WING A/I to OFF with no ICE message and airspeed > 230 kts.

 

Long story short: In the real aircraft WING A/I is the main culprit for de-/increased engine thrust in flight - on ground there is no such effect. So, this subject (including FLEX thrust) needs to be reworked by AS.

 

  • Upvote 2
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...