PROF mode problems

[themasterWookie 17]

Hi everyone,

 

I recently was flying on a short flight when I started facing problems with the vertical profile mode. When I had established my cruise altitude of FL330, the profile altitudes of waypoints I had not yet reached started to increase, causing the altitude on the PFD to become white (HOLD was still magenta, which meant that PROF mode was on). I kept the aircraft leveled at 330, not allowing it to ascend to the altitudes the FMC was calculating. Because of this, the T/C indication on the F-PLN page started to move back, and the aircraft wasn't able to execute the descent, as it had not even reached its top of climb point. Is this indicated cruise alt increase because of fuel consumption? I'm a bit confused right now, so can someone help me out?

[xkoote 57]

Not sure what you did wrong. But if you find yourself in that bind again. What I do is select altitude hold to make sure the FMS won't punish me for making altitude inputs while in CRZ mode. I assign the altitude I want to stay at in the INIT page. In your case input 330 in cruise levels. Make sure your altitude readout also displays 33000 and then select PROF mode on the FCP.

 

Before departure remember to set up the FMC's INIT page the way you want to fly. Especially altitudes. Set up your initial cruise altitude followed by additional step climbs you desire. Double check that the initial cruise altitude you inserted is indeed possible.

 

The MD-11 has a nasty tendence (for me at least) to deviate from altitude when toying around with cruise altitudes. Especially when a step climb was inserted. So to avoid any problems switch to the basic altitude hold mode, make your changes in the INIT page and re engage PROF mode after.

 

Hope it helps,

 

Xander

[sheepfu 3]

The altitude should never exceed the value set in the MCP. If you are supposed to be flying at 330 for a certain leg than that altitude should be in your MCP window. If the FMC requests a step climb. Increase the altitude setting on the MCP and then press the PROF button.

[PHXMD-11 86]

If the FMC requests a step climb. Increase the altitude setting on the MCP and then press the PROF button.

 

Just set the altitude in the FCP. Step climbs are automatic and you don't need to press the PROF button again.

 

The MD-11 has a nasty tendence (for me at least) to deviate from altitude when toying around with cruise altitudes.

 

If you have altitudes of 330 and a step climb to 350 planned on the INIT page, she should hold 330 until you set the altitude to 350 and then hold that altitude. Not sure what's going on with your MD-11.

 

Is this indicated cruise alt increase because of fuel consumption?

 

No. If you just have 330 planned on the INIT page, the aircraft should maintain 330 until the top of descent. She will not perform automatic step climbs if you have not ordered it on the INIT page.

[xkoote 57]

There's nothing going on with any of the MD-11's. In normal circumstances the FCP behaves like you want it to. But if for example you programmed step climbs, have your altitude set as the final altitude in your read out, then change your mind regarding your altitude choice (e.g. You want to maintain present level all the way to destination) and you change it in the INIT page for some reason the MD-11 will command a profile climb to IIRC max altitude. I don't remember exactly because with the way I now reprogram the FMC I don't see it happening again. But for someone still learning the FCP you may find that it will start climbing even though you don't want to.

 

Xander

[themasterWookie 17]

I check the INIT page every time before taking off. As I was flying this flight with no step climbs in the cruise, I only entered one 330 on the INIT cruise levels section. I don't know if entering 330 in all the sections would help eliminate this problem. I've flown like a dozen flights in which I did not face this problem, I don't know what happened this time. I could just execute the descent by disabling PROF and using the FCP alt and vertical speed, but that would be pretty inaccurate.

[PHXMD-11 86]

I don't know if entering 330 in all the sections would help eliminate this problem.

 

Just enter it once. That tells the FMS you want to fly and maintain FL330.

 

I could just execute the descent by disabling PROF and using the FCP alt and vertical speed, but that would be pretty inaccurate.

 

Pull the altitude knob to initiate a descent at the selected IAS/Mach. Just like the FL/LVL CHG mode on a Boeing.

[jshoberg 0]

Hi everyone,

 

I recently was flying on a short flight when I started facing problems with the vertical profile mode. When I had established my cruise altitude of FL330, the profile altitudes of waypoints I had not yet reached started to increase, causing the altitude on the PFD to become white (HOLD was still magenta, which meant that PROF mode was on). I kept the aircraft leveled at 330, not allowing it to ascend to the altitudes the FMC was calculating. Because of this, the T/C indication on the F-PLN page started to move back, and the aircraft wasn't able to execute the descent, as it had not even reached its top of climb point. Is this indicated cruise alt increase because of fuel consumption? I'm a bit confused right now, so can someone help me out?

I know I'm four years late but this is exactly the problem I'm having with one particular short flight...KOAK to KPDX on the MD-11. I don't seem to have this issue with other (longer) flights. I've tried numerous times to keep the the VNAV from wanting to increase the CRZ during the flight including wiping it out and re-entering it. It will start with everything correct in the F-PLAN, i.e.,  FL360 with no step climbs. Somewhere during the flight it will change to some unusual level, usu. FL375! And then the decent problems follow. I thought it was this flight in particular because it was SID to STAR with nothing in between. I added a waypoint in between but it didn't help. Oh well, must just be a fluke.

 

Chirag, you aren't the only one.

 

 

Jim Shoberg

[pcubine 143]

it will change to some unusual level

What changes first? The altitude window or the MD-11's altitude. The F-PLAN INIT page has 360 enter in cruise levels line. The PFD altitude tape shows 36000 and above that is displayed in magenta PROF 36000 and below that HOLD 36000. The MD-11 shows all this. Is that correct?

[jshoberg 0]

The PROG page will show the next, and subsequent, waypoints as changed to FL375. The F-PLAN page still shows FL360. The airliner then pushes the new FL ball for the rest of the flight..

 

 

 

 

The PFD altitude tape shows 36000 and above that is displayed in magenta PROF 36000 and below that HOLD 36000.

 

I'm not in front of it right now but I believe this is correct

[pcubine 143]

The PROG page will show the next, and subsequent, waypoints as changed to FL375.

For right now, forget the PROG page. What was the altitude of the plane?

[jshoberg 0]

For right now, forget the PROG page. What was the altitude of the plane?

 

The altitude on the AFDS panel is set at 36000. So the plane won't ascend further although it wants to.

[pcubine 143]

So the plane won't ascend further although it wants to.

I would like to try this flight and see what happens. When you have a chance I would appreciate the payload, fuel at release, CI, departure and arrival runways, and the SID and STAR used. I thought that maybe on such a short flight the plane was still climbing when it went past the T/D and that blew the FMS' mind. But it ran okay using a good flight planner. So that was not the problem.

[pcubine 143]

So the plane won't ascend further although it wants to.

Thanks for sending me the route and other information that I requested. The flight was normal with no indication in the FMS or on the instruments that the plane wanted to climb higher. Did the route come from a saved NGX route or was it built and exported to the FMS by PFPX? I have attached two screenshots showing the cruise and just before descent.

Cruise

Just Before Decent

[jshoberg 0]

I really don't know what the cause was originally. It hasn't happened again since I posted. I appreciate your time on this and apologize for wasting it.

 

I have much bigger problems today...I installed PMDG 777-200.

 

ETA: this is the original flight plan generated by SimBrief.com

 

HUSSH2 GRTFL MACHU TMBRS2