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Autopilot does not reach cruise on derated climb

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I noticed this my last few flights and I wonder if anyone knew how I could fix this. I'll do a derated takeoff with a climb 2. I takeoff fine and I engage my autopilot. Cruise is set to be FL220. The climb progresses as scheduled and the engines kick in for a stronger climb at the higher altitude. The problem is that when I get up to around FL220 my panels show that I am still in climb mode and it keeps pushing back my TOC on the map. This happens at waypoint after waypoint where I am supposed to be at cruise. I only started noticing this with derated takeoffs. I am not programming the required temp into the FMC as I don't have topcat. Could this lack of info be causing the issue?

 

Chris

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it has nothing to to about topcat. So do you use TO-2 on takeoff and CLIMb-2 right ?  try to use CLIMB-1 OR CLIMB and see what happens

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Make sure you're in VNAV and not another vertical speed mode. You won't automatically flip to CRZ thrust outside of VNAV.

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Make sure you're in VNAV and not another vertical speed mode. You won't automatically flip to CRZ thrust outside of VNAV.

vnav is active. I will check to see what happens with climb one. 

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Altimeter set to 29.92?

Yes, set to standard after passing transition at fl180. 

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I think in the panel or aircraft config there is an option for a derate washout altitude? Have you tried changing that? Standard, I think, is 12000' (though I think the NGX allows you to disable this or set it higher). It would be interesting to see if the derated thrust reverts to normal CLB at 12K and/or if it affects the behavior you describe.

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? Standard, I think, is 12000' (though I think the NGX allows you to disable this or set it higher). It would be interesting to see if the derated thrust reverts to normal CLB at 12K and/or if it affects the behavior you describe.

This altitude is set to 15000' on every 737 with no exception.

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This altitude is set to 15000' on every 737 with no exception.

 

Thanks for clarifying.

 

If he's climbing to FL220, then his CLB-2 derate should automatically have washed out well before this point, no?

 

EDIT: Just tried this myself in the stock configured NGX 737-800...TO-2 with CLB-2...VNAV climb to FL220. Derate washed out at 15K, then CLB up to FL220 and then flipped over to CRZ thrust. Not sure what the OP is doing or maybe has configured differently.

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Just tried with climb one and had same exact result. It switches to normal climb at 15000 but when it gets to fl220 it refuses to switch to cruz thrust. There is an fmc message to reset mcp alt but its already set at 22000. Not sure why I am getting that message. FMC is setup for fl220 cruise.  

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Just tried with climb one and had same exact result. It switches to normal climb at 15000 but when it gets to fl220 it refuses to switch to cruz thrust. There is an fmc message to reset mcp alt but its already set at 22000. Not sure why I am getting that message. FMC is setup for fl220 cruise.  

 

Can you post your flight plan? I wonder if your cruise altitude is too high...i.e. your T/D *precedes* your T/C. Reset MCP Altitude usually appears when the VNAV wants to descend but the MCP hasn't been set. It seems like by the time you arrive at your cruise altitude, your descent window has already passed - hence the FMC message.

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Can you post your flight plan? I wonder if your cruise altitude is too high...i.e. your T/D *precedes* your T/C. Reset MCP Altitude usually appears when the VNAV wants to descend but the MCP hasn't been set. It seems like by the time you arrive at your cruise altitude, your descent window has already passed - hence the FMC message.

In my flight plan there are about 4 waypoints at the cruise level of FL222. Maybe a 100NM between TOC and TOD. What is interesting is when I hit TOD all of a sudden that is when the cruise kicks in. I will try a slightly longer flight tomorrow and see if that makes a difference. 

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Are you online when this occurs?

 

FSInn has a faulty weather injection problem where temp increases with altitude.  This can result in very unrealistic conditions, which result in what you're seeing.  Make sure to disable FSInn weather entirely.

 

I think Opus used to do this (or similar) at one point.  I don't think the current version has this issue, so make sure you're running the latest version of Opus, if you use that.

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In my flight plan there are about 4 waypoints at the cruise level of FL222.

 

222?

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In my flight plan there are about 4 waypoints at the cruise level of FL222

FL222? What does your OAT read? If you keep pressing 'B', what kind of barometric pressures are you getting? Are they stable or fluctuating?

 

Please post your flight plan so others may try it. Cropped screenshots of your FMC pages might also be helpful.

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Sorry was tired after last flight. I meant fl220. I do fly online,but the times I noticed this issue was in offline flying. I do use opus and think I have the latest version but I will check again. I do have sp1.

I will try the flight again later today and monitor the oat and try to take some screenshots and post my flight plan. In terms of baro setting, I set it before takeoff and once I pass through Fl180 I click standard which I think is 2992. Is this the proper procedure?

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I am not programming the required temp into the FMC as I don't have topcat. Could this lack of info be causing the issue?

 

It's not a required temp.

 

On that page, you may:

  1. Leave it blank (full rated thrust takeoff)
  2. Enter an assumed temperature to use the Assumed Temp Method (ATM)
  3. Select a derated thrust option; or
  4. A combination of 2 or 3

From the sounds of it, it seems like you aren't correctly setting your cruise altitude, either on the MCP or the FMC.  Both of those need to have the information in order to recognize that you've reached cruise.

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I would also add that I am right on the verge of going over speed, so that may play some part in it? I tried lowering my speed to .78 but it didn't make a difference. According to my altimeter I'm flying level at 22000.

I would also add that I am right on the verge of going over speed, so that may play some part in it? I tried lowering my speed to .78 but it didn't make a difference. According to my altimeter I'm flying level at 22000.

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I would also add that I am right on the verge of going over speed, so that may play some part in it? I tried lowering my speed to .78 but it didn't make a difference.

 

Probably not.  It may be related, but not a cause.

 

 

 


According to my altimeter I'm flying level at 22000.

 

Right.  Again, the aircraft needs to know what your cruise altitude is going to be.  This is set on the PERF INIT page, and should also be matched by the altitude window of the MCP.  If either one of those is not set properly, it can cause issues.

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Last time I saw something like this, the problem was the user had loaded the acft with weight units set in KG instead of Lbs, and the jet was massively overweight.

 

Edit: if your speeds are way high, check the outside air temp--if it's crazy high (as can happen with a misbehaving wx add-on program) that would explain both the high indicated airspeed and the inability to reach cruise, as the computed climb power setting would be far too low.  At FL220 standard OAT would be ~ -29 deg C.

 

Cheers

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Right.  Again, the aircraft needs to know what your cruise altitude is going to be.  This is set on the PERF INIT page, and should also be matched by the altitude window of the MCP.  If either one of those is not set properly, it can cause issues.

 

Yep they are both definitely set and match up.  

Last time I saw something like this, the problem was the user had loaded the acft with weight units set in KG instead of Lbs, and the jet was massively overweight.

 

Edit: if your speeds are way high, check the outside air temp--if it's crazy high (as can happen with a misbehaving wx add-on program) that would explain both the high indicated airspeed and the inability to reach cruise, as the computed climb power setting would be far too low.  At FL220 standard OAT would be ~ -29 deg C.

 

Cheers

Thanks for the headsup on what the OAT should be. I did notice on one flight a sudden burst of overspeed. Like it just jumped up suddenly. I will definitely keep an eye on it this next flight. The issue of weight is interesting. I didn't change the units, but I do have the default amount of fuel on board. Normally I use only the specific amount of fuel that I need based on pfpx calculations, but since I have been doing these last couple of flights to test vas usage and try to reduce it I have just been going with whatever is in the tank. For my next flight I will use a specific fuel calculation. 

 

Chris

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