Sign in to follow this  
leftseatguy

Not easy to maintain level flight without autopilot engaged

Recommended Posts

I'm unsure whether its just me or if other people have similar problems but I would be interested to hear your comments about the following:

 

My usual practice with the 737NGX is to take off and climb to initial cleared level with autopilot off, making use of the flight director bars to monitor my progress. However, when I reach the cleared level I find I am constantly having to adjust my pitch to try and hold the altitude. I realise that the trim setting is there to control speed rather than altitude so adjusting the trim seems to have little or no effect on the pitch and therefore my ability to keep the aircraft level, whereas in an GA aircraft it is course normal practice to adjust the elevator trim as required for each vertical manoeuvre, such as when levelling off after a climb or descent etc.

 

Actually I raised this question at a recent meeting of my local flight simulator group and the answer that I received was that real world pilots have the same problem which is why hand flying in level flight is more often done with autopilot engaged. I should add that I normally hand fly the final approach and landing as much as I can, because that's much more fun!

 

Comments please?

 

Dennis Hickman

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

IRL, its very easy to maintain straight and level with out using an autopilot.

 

In a desktop simulator it can be easy with the right controls and lots of practice. The variable of weather is of course a factor, but it takes lots of practice to become comfortable to fly without an autopilot.   

Share this post


Link to post
Share on other sites

Hello Denis, what altitude are you at having difficulty hand flying ? With good contros and practice you should be perfectly able to do it up to 10,000 ft and even higher. At the flight levels, it is very difficult because of thin air.

Share this post


Link to post
Share on other sites

Hello all,

 

What are you people talking about? What does altitude has to do with hand flying??? IAS is IAS be it at 50 or 50.000 feet and a trimmed aircraft is trimmed regardless of altitude.

 

So, noise aside, if you ever lay you hands on a REAL airplane there is only one thing to know when it comes to AVIATE: pitch is speed and power is altitude. Power or not, it will always pitch for a given speed.

 

As a real pilot, NO, we don't have that problem, unless the aircraft designers have really screwed it up (they don't). NATURAL stability arround all axes is one of the most important design goals regardless of aircraft size or speed. Of course I would not cross an ocean on manual, but it can be perfectly flown on manual though.

 

If you want to learn more, Aerodinamics for Naval Aviators is a great book that will give you a lot on this subject.

 

Ionut (John) G. Micu

  • Upvote 1

Share this post


Link to post
Share on other sites

Hello all,

 

What are you people talking about? What does altitude has to do with hand flying??? IAS is IAS be it at 50 or 50.000 feet and a trimmed aircraft is trimmed regardless of altitude.

 

So, noise aside, if you ever lay you hands on a REAL airplane there is only one thing to know when it comes to AVIATE: pitch is speed and power is altitude. Power or not, it will always pitch for a given speed.

 

As a real pilot, NO, we don't have that problem, unless the aircraft designers have really screwed it up (they don't). NATURAL stability arround all axes is one of the most important design goals regardless of aircraft size or speed. Of course I would not cross an ocean on manual, but it can be perfectly flown on manual though.

 

If you want to learn more, Aerodinamics for Naval Aviators is a great book that will give you a lot on this subject.

 

Ionut (John) G. Micu

John.

 

Sorry, I just had to laugh when I read your first statement.  Yes, trim is vitally important and if you find that you need to set trim and throttle so much, then switch on the autopilot.  Flying a tubeliner takes a whole lot more practice and focus, compared to a GA aircraft, simulator or not.  The OP is pretty much on target with stating that takeoff and landing can be done by hand, but everything else is much easier and less of a hassle with LNAV and VNAV active with the autopilot.

 

-Jim

Share this post


Link to post
Share on other sites

One of the things a lot of people forget about, since a lot of the tubeliners are LNAV/VNAV machines, is that you are constantly trimming if you're not on AP.

 

Here's one of my recent flights:

http://flightaware.com/live/flight/N571DS/history/20150923/1541Z/KSHD/0A9/tracklog

 

Note that there are slight altitude deviations here and there, simply based on how the airmass is behaving, the density of that airmass, the accuracy of how I'd trimmed before, and the interaction between speed and lift. Of course, part of that is your own attention, too. If you're thinking "well, of course a tiny plane without AP is going to be affected by airmass changes," then have a look at one of the local C-47s that flies around. You can see a little pilot induced oscillation about 1/3 of the way through the flight:

http://flightaware.com/live/flight/N47E/history/20150830/1539Z/KHFD/KPOU/tracklog

 

Trim, even at cruise, is not "easy" simply because it's "straight and level." It's actually a decent amount of work to remain on altitude.

Share this post


Link to post
Share on other sites

I realise that the trim setting is there to control speed rather than altitude so adjusting the trim seems to have little or no effect on the pitch and therefore my ability to keep the aircraft level, whereas in an GA aircraft it is course normal practice to adjust the elevator trim as required for each vertical manoeuvre, such as when levelling off after a climb or descent etc.

 

That trim for airspeed philosophy isn't working for you. I would suggest pitch for the level off attitude and then  trim away the pressure on the yoke. It's much harder in a sim with no feedback.

 

You're fighting the plane. Set the pitch attitude you need and then trim it out.

Share this post


Link to post
Share on other sites

Hello all,

 

What are you people talking about? What does altitude has to do with hand flying??? IAS is IAS be it at 50 or 50.000 feet and a trimmed aircraft is trimmed regardless of altitude.

 

So, noise aside, if you ever lay you hands on a REAL airplane there is only one thing to know when it comes to AVIATE: pitch is speed and power is altitude. Power or not, it will always pitch for a given speed.

 

As a real pilot, NO, we don't have that problem, unless the aircraft designers have really screwed it up (they don't). NATURAL stability arround all axes is one of the most important design goals regardless of aircraft size or speed. Of course I would not cross an ocean on manual, but it can be perfectly flown on manual though.

 

If you want to learn more, Aerodinamics for Naval Aviators is a great book that will give you a lot on this subject.

 

Ionut (John) G. Micu

Well I recall a few occasions where I had an autopilot fail at FL410 in the older Learjet 30 series and had to hand fly for the rest of the flight for an extended period of time.Yes it can be done but requires concentration at that altitude, a small pitch change could result in an altitude deviation.You don't spend time looking out the window but have to fly it on instruments. We had at late serial number Learjet 25 that was certified to FL510, I tried on a couple of deadhead flights to see how high we could get it, the autopilot was wallowing around at FL470 in smooth air.I sure as hell would not want to have had to hand fly it at that altitude for any amount of time. BTW, the aircraft required a mach trim system functioning above .72 without the autopilot engaged because of the lack of inherent pitch stability.They were a dream to hand fly in dense air, leave the hand flying to computers at the high flight levels unless you are Chuck Yeager.

 

Gary Stewart

Share this post


Link to post
Share on other sites

Yes of course that the airplane is harder to trim and therefore harder to fly at the flight levels done by hand without an autopilot. The poster that pointed otherwise must be a flyer of some other kind.

Share this post


Link to post
Share on other sites

Well I recall a few occasions where I had an autopilot fail at FL410 in the older Learjet 30 series and had to hand fly for the rest of the flight for an extended period of time.Yes it can be done but requires concentration at that altitude, a small pitch change could result in an altitude deviation.You don't spend time looking out the window but have to fly it on instruments. We had at late serial number Learjet 25 that was certified to FL510, I tried on a couple of deadhead flights to see how high we could get it, the autopilot was wallowing around at FL470 in smooth air.I sure as hell would not want to have had to hand fly it at that altitude for any amount of time. BTW, the aircraft required a mach trim system functioning above .72 without the autopilot engaged because of the lack of inherent pitch stability.They were a dream to hand fly in dense air, leave the hand flying to computers at the high flight levels unless you are Chuck Yeager.

 

Gary Stewart

"Center, Lear123 request block 45oh 51oh.

 

And direct destination "

Share this post


Link to post
Share on other sites

Proof of this increased difficulty in hand flying at high altitude is the RVSM requirements. In addition to special altimeters and air data computers, more precise flying autopilots are also on the minimum equipment list.

 

Personally, I don´t think that I can hand fly as precise as the old autopilots, let alone the new ones.

Share this post


Link to post
Share on other sites

Hello all,

 

pitch is speed and power is altitude.

John,

 

The next time you are setting at the end of the runway in your airplane about to take off, start pumping the yoke back and forth and let me know when you reach flying speed. :-)

 

blaustern

Share this post


Link to post
Share on other sites

John,

 

The next time you are setting at the end of the runway in your airplane about to take off, start pumping the yoke back and forth and let me know when you reach flying speed. :-)

 

blaustern

Obviously it's like getting into orbit! You just have to go down slower than the earth is falling away. And that's why you have to push down. ;)

Share this post


Link to post
Share on other sites

The 767 is mad easy to hand fly, at altitude, and stay relatively level. Within 5 feet? No, but the needle is about 20 feet wide anyway. However, the catch is that your thumb would get very tired!

Share this post


Link to post
Share on other sites

Hi guys! I seem to have really started quite a lot of responses to my original question! Thanks very much all.

 

For what its worth I just thought I would give you a small update on my latest attempt to hand fly for an fairly extended period the PMDG 737-800ngx. I took off from EGKK with an average sort of load and fuel and climbed to 10,000 feet without any problems without autopilot. Having levelled off at that altitude I reduced the throttle setting to what I thought would be an appropriate setting for a cruise at that altitude (just a rough guess). Thereafter I did my best to hold that level by making adjustments to the pitch every time I saw the altitude changing up or down. I found this very difficult to achieve until I started trying to use the trim to reduce the tendency to climb or descend. What then happened was that I realised that was not in control of  the speed. So I am beginning to realise that its really a balancing act which has to be practised to coordinate yoke, throttle and trim in order to get the aeroplane to fly straight and level. Having flown single engine light aircraft (for real ) I can certainly understand why this is. I must admit that at first I didn't find it easy to fly straight and level, but it does seem a lot more difficult in a commercial airliner and is going to need a lot more practice on my part!

 

Just as a footnote, I would just add that I managed to get the aeroplane back on the ground (at the airport) with a little help from ILS. So the whole flight was manual  - almost!!

 

Dennis Hickman 

Share this post


Link to post
Share on other sites

Hello all,

 

Thank you to all of those who responded to my post. Please, don't get me wrong, I know that is very hard to hand fly at high altitudes, I was just trying to say that it can be done.

 

As for the power pitch equation, of course that once you are trimmed and power is constant all that is left to do is to make small elevator inputs to keep it at level (AP does it too) and that indeed is a lot of work because is has a great effect and very rapidly.

 

Wilhelm Brucken: I really like your humor :) I hope you are not implying that the statement is incorrect ...

 

Ionut (John) G. Micu

Share this post


Link to post
Share on other sites

Just as a footnote, I would just add that I managed to get the aeroplane back on the ground (at the airport) with a little help from ILS. So the whole flight was manual  - almost!!

 

Dennis Hickman

 

KUDOS, Dennis.

It is fairly difficult to handle in the three dimensions of flight. And you're right, it's a balancing act between pitch and power.

I just recently had a complete auto flight system failure at FL310, but fortunately for me, I was only a few miles from TOD. Even then, it was a handful.

Share this post


Link to post
Share on other sites

Wilhelm Brucken: I really like your humor :) I hope you are not implying that the statement is incorrect ...

 

Ionut (John) G. Micu

John,

 

It is not a joke. I have spent many a cold, dark night up on R220 drinking coffee and talking about flying. One of the Captains I flew with had over 30,000 hours in heavy jets. He believed that speed is controlled with power and altitude with pitch. I also believe it. Of all the instruments used for flying, especially flying IMC, power is probably the most important.

 

blaustern

Share this post


Link to post
Share on other sites

Wilhelm,

 

With all due respect for your respective experiences, allow me to disagree with you gentleman. When you are in the air without power, you can maintain any airspeed you wish but cannot maintain altitude.

 

Regards,

Ionut (John) G. Micu

Share this post


Link to post
Share on other sites

There are two distinct groups who have debated this very topic for years and years. There is some truth to both sides of the discussion. No need to run off on that tangent here.

Share this post


Link to post
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
Sign in to follow this