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jwcrusan1918

Trimming for Level Flight not functioning as expected

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So I've recently had time to do some more longer flights on FSX given the recent situation and all, and I noticed one thing has changed during my recent flights. I've been flying a default 737 across the country, and today I went from KLAX to Honolulu International in a default 747 -- and at some point the 737 started not flying level, and the 747 did the same today. So I tried to trim both the aircraft to fly level, by trimming the elevators downward, however it did not yield the expected result. What happened was the nose leveled out, however the aircraft began to lose altitude, and the autopilot put the trim back where it was and corrected the altitude. So I disengaged the autopilot and tried the same. The same result had occurred with the exception of the autopilot resetting the trim of course. I'm a little confused mostly because this never used to be a problem before, and also to the best of my knowledge it seems that adjusting the trim is what you're supposed to do to get the aircraft to fly level. If anyone can offer up some help to help me solve this minor issue, it would be greatly appreciated. 

If it is of importance, I have the cruising speeds and altitudes for both aircraft I was at in which I tried this. 

B744 - FL350, Mach 0.85

B738 - FL300, 280 kts

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43 minutes ago, jwcrusan1918 said:

So I tried to trim both the aircraft to fly level, by trimming the elevators downward, however it did not yield the expected result. What happened was the nose leveled out, however the aircraft began to lose altitude, and the autopilot put the trim back where it was and corrected the altitude.

This action you described as being incorrect is actually correct. Flying level would actually be described as not gaining or losing altitude or a 0 (zero) on the VSI - vertical speed indicator.

It’s not uncommon when you get to higher altitudes and still have some weight of fuel on board and lower air speed that the aircraft has the nose pitched up a bit to hold the altitude, however it shouldn’t be pitched up at severe amount like 5% or more. If I recall, it’s been a while since I’ve flown, but typical should be about 2.5 degrees or so.

That being said, if you flying around at FL350 with the nose pitched up 5 degrees or more at .85 mach, you probably should be at a lower altitude. That’s why airliners sometime do step climbs on long hauls where they fly the first segment at perhaps FL270 or 280, depending on which direction your going, then after some fuel is burnt off, will step up to FL300-310, then later to FL340-350, etc. 

In other words, if your fully loaded or close to fully loaded, you just don’t go from takeoff to FL350 right off the bat without losing some weight by fuel burn off.

In addition, you might be loading a lot more fuel than is needed. Depends on the winds, distance, reserves, etc. The default planner might give an appropriate amount of fuel but I don’t think it takes the upper level winds into effect. That’s where addons like an aftermarket flight planner and weather engine like Active Sky come in handy because they will give a more accurate fuel load based on the winds at altitude, direction flown, temps, etc.

Hope this helps and clarifies it a bit for you.

BTW, I don’t think I’ve ever flown any airliners at any speed or altitude where the plane was ever at a level or zero angle of attack with a VSI reading of zero. You’ll probably always have at least a degree or two of pitch up.

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To quote directly from an article about the MD-11 (as an example)

https://airwaysmag.com/best-of-airways/twilight-md-11/

Quote

“The triple-seven is the airplane I like, but the MD-11 is the airplane I love,” said Marije, a KLM senior flight attendant. “I enjoyed spending time with my colleagues in the rear galley, which was so large we could have thrown parties, danced and even jumped if we had wanted to,” she noted. “However, pushing a cart from the rear to the front while the airplane cruised was quite the workout!” she explained, making reference to the noticeable pitch-up attitude the MD-11 was known for during its cruise setting.

My italics.

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16 hours ago, cmpbellsjc said:

This action you described as being incorrect is actually correct. Flying level would actually be described as not gaining or losing altitude or a 0 (zero) on the VSI - vertical speed indicator.

It’s not uncommon when you get to higher altitudes and still have some weight of fuel on board and lower air speed that the aircraft has the nose pitched up a bit to hold the altitude, however it shouldn’t be pitched up at severe amount like 5% or more. If I recall, it’s been a while since I’ve flown, but typical should be about 2.5 degrees or so.

That being said, if you flying around at FL350 with the nose pitched up 5 degrees or more at .85 mach, you probably should be at a lower altitude. That’s why airliners sometime do step climbs on long hauls where they fly the first segment at perhaps FL270 or 280, depending on which direction your going, then after some fuel is burnt off, will step up to FL300-310, then later to FL340-350, etc. 

In other words, if your fully loaded or close to fully loaded, you just don’t go from takeoff to FL350 right off the bat without losing some weight by fuel burn off.

In addition, you might be loading a lot more fuel than is needed. Depends on the winds, distance, reserves, etc. The default planner might give an appropriate amount of fuel but I don’t think it takes the upper level winds into effect. That’s where addons like an aftermarket flight planner and weather engine like Active Sky come in handy because they will give a more accurate fuel load based on the winds at altitude, direction flown, temps, etc.

Hope this helps and clarifies it a bit for you.

BTW, I don’t think I’ve ever flown any airliners at any speed or altitude where the plane was ever at a level or zero angle of attack with a VSI reading of zero. You’ll probably always have at least a degree or two of pitch up.

Thanks for the reply -- I used to play FSX when I was younger and I'm just getting back into it after I upgraded to a better computer (and got older and thus more mature and patient lol) and I'm always learning more about the actual sim and things like we're talking about here. I'll definitely look more into cruising altitudes and weather as well. Thanks again! 

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3 hours ago, jwcrusan1918 said:

Thanks for the reply -- I used to play FSX when I was younger and I'm just getting back into it after I upgraded to a better computer (and got older and thus more mature and patient lol) and I'm always learning more about the actual sim and things like we're talking about here. I'll definitely look more into cruising altitudes and weather as well. Thanks again! 

I’d suggest, if you’re really interested in learning the mechanics of flight to start at the bottom like all pilots do and work on flying the Cessna 172 and make even do the lessons. In real life we don’t go from zero aeronautical experience, flight school and low level training, right to flying the 737 or 747 without knowing the basics. Granted it might not be a fun or exciting but at least you’ll get a grasp of flying by hand and knowledge that comes from it.


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1 hour ago, cmpbellsjc said:

I’d suggest, if you’re really interested in learning the mechanics of flight to start at the bottom like all pilots do. Granted it might not be a fun or exciting but at least you’ll get a grasp of flying by hand and knowledge that comes from it.

Actually, I'd disagree with that sentiment, or rather the last bit of it. Learning to do something well, particularly something which is not a commonplace skill such as flying an aeroplane, is almost always a very rewarding experience, and for anyone who really likes aeroplanes, that is fun and exciting. When you learn to operate an aeroplane very accurately and skillfully, it gives you a real sense of achievement; you are taming a machine, mastering it, gaining a skill which most people out there do not possess.

Most people see action movies where a pilot is incapacitated and think: 'oh my god what would I do?', whereas if you get great at handling an aeroplane manually, you'll think: 'yeah, that'd be no problem'. That sets you apart from most people. If you know how one aeroplane flies and fully understand exactly what is keeping it in the air, you'll know how they all do that, and that is a special feeling. One which all pilots have.

So getting in a little Cessna or some such and doing a bunch of circuits, until you can keep the thing nailed on 1,000 feet AGL on the downwind by knowing the correct pitch and power settings, rolling it out on perfectly-coordinated right angle turns where the ball looks like it is glued in the middle of the slip indicator throughout, whilst keeping the exact altitude or rate of descent/ascent you want, then planting that thing perfectly on the centreline, smack bang on the aim point of the runway with the wings stalling a moment after your wheels are down, even in a simulator, is a nice challenge to master. And it is one which will serve any flight sim fan well when they jump in any other virtual aeroplane.

Flying is a great adventure even when you're just doing circuits and bumps in a little GA aeroplane. After all, it's what people could only have dreamed of doing up until just over a century ago.

Edited by Chock
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Alan Bradbury

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1 hour ago, Chock said:

Actually, I'd disagree with that sentiment, or rather the last bit of it. Learning to do something well, particularly something which is not a commonplace skill such as flying an aeroplane, is almost always a very rewarding experience, and for anyone who really likes aeroplanes, that is fun and exciting

Al, actually I think we both agree but I didn’t state the context in which I said “it might not seem fun or exciting.”

When said that I meant in the sense that for a lot of people who are new to simming and/or treat it more like a game than a sim, they tend to bypass the learning stage of starting with a single engine prop and to the jets straight away without first learning the fundamentals of flight. Most likely the reason being that 100kts is not as fun as 400kts or just want to fly something huge in comparison to a SEL. That was what I meant in a bit shell.

Thats being said, in real life, flying any SEL types even at 70kts is enormously fun and enjoyable, but I don’t think it translates as such in the sim for those who haven’t done in it real life. Even for myself, who’s never flown anything IRL larger than a 172, doing it the sim can sometimes be a bit dull since we don’t have the sensory feedback and of course risk, that we have IRL.

 

 

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