Hand flying Boeing 737

I was practicing hand flying the fsx Boeing 737 at low speeds and came across something a bit odd.

 

I was making turns at 5000 ft at a speed of 180 and 5 degrees of flaps. I started out using AP to get to altitude and speed. I then turned off AP and started practicing turns and noticed after I completed the turn and leveled off that my original speed was now about 165 or lower. I was careful to set N1 at the same setting as when AP was on ( I set speed using auto throttle).

 

Is this typical or am I doing something wrong ?

I notice that even flying with A/P and A/T set, my aircraft tend to lose some airspeed while making turns. At 180 knots, I would tend to use 10 degrees flaps.

I wasn't surprised that I lost speed in a turn. What surprised me is that when I returned to straight and level flight I never regained my original speed even after several minutes of straight and level flight.

I wasn't surprised that I lost speed in a turn. What surprised me is that when I returned to straight and level flight I never regained my original speed even after several minutes of straight and level flight.

 

OK, sorry, So when using the A/T you are setting N1 to a certain percentage? Would it make a difference to set it to hold 185 knots IAS?

It's perfectly normal for a plane to slow a bit in a turn. The steeper the bank, the great the loss, generally. Think about aerodynamics: When you go into a turn, once you bank over, the lift of the wings is no longer straight up, but now tangential (big word for the day!), and is being used to both lift the plane, and pull the plane around the corner. You need to increase the power slightly to compensate.

If you think about the lift+thrust=load+drag equation, when you go into a bank for a turn, your lift decreases (tangential, remember? :) ), so you need to increase thrust to compensate for it, too keep the equation balanced.

Once you roll out, you can set it back to what it was for cruise, now that lift, thrust, drag, and load are all balanced again.

Mathmatics explains all :D

Does this help at all?

Pat☺

To really hold the speed close, you need to constantly adjust the throttles.

You can't just leave at a certain N1 and expect the speed to hold when maneuvering.

Even straight and level can require slight tweaking, as well as descending for landing, etc.

You should be able to keep the speed within 5 knots as long as no wind mayhem.

I can often almost keep it right on the money if I really want to. For many years SWA

did not use A/T at all.

When using AT with AP on N1 is set for you. All I did was set the same N1 value manually when I was flying straight and level with AT and AP off.

Right. But even the A/T has to constantly adjust the throttle, same as when hand

flying the throttle. It's not going to hold the same N1 if the plane starts to slow or

speed up. You just captured the N1 at that one period in time.

Think of it the same as driving a car through hills.. Whether foot or cruise control,

the throttle is going to be constantly changing to hold the same speed.

Right. But even the A/T has to constantly adjust the throttle, same as when hand

flying the throttle. It's not going to hold the same N1 if the plane starts to slow or

speed up. You just captured the N1 at that one period in time.

Think of it the same as driving a car through hills.. Whether foot or cruise control,

the throttle is going to be constantly changing to hold the same speed.

 

 

Ok that makes sense now. After my long layoff I'm going back and redoing my pitch and power settings. I spend more time flying props but I do like the 737 and the Bombardier. I need to remember jets are very different animals.

 

I am a bit rusty after my long layoff, but it will come back -I hope.

***I need to remember jets are very different animals.***

 

No they're not, the exact same principles apply to any aircraft.

 

Glider, prop or jet.

 

Just different numbers fit the same equation(s)

Ok that makes sense now. After my long layoff I'm going back and redoing my pitch and power settings. I spend more time flying props but I do like the 737 and the Bombardier. I need to remember jets are very different animals.

 

I am a bit rusty after my long layoff, but it will come back -I hope.

 

You will be surprised by how fast it will come back. That's why I suggested using A/T set to knots indicated. It will use whatever "thrust" setting it needs to maintain the speed.

Ok that makes sense now. After my long layoff I'm going back and redoing my pitch and power settings. I spend more time flying props but I do like the 737 and the Bombardier. I need to remember jets are very different animals.

 

I am a bit rusty after my long layoff, but it will come back -I hope.

 

The same rules apply to a recip. plane. I just flew a .5 hour test flight with the default DC-3.

 

At 34" pressure & 2500 RPM, 1,000 ASL I was cruising at 175 Straight and Level according to the portable GPS. In a standard rate turn of 180* while holding altitude I bled off to 158 & it took several miles to rebound to 175. I manually set the weather to zero kts. wind & made several turns into and out of all four quadrants. The results were the same.

 

However I will say I was surprised. It's been 50 years since I've been in the right seat of a Marine R-4. But if I recall correctly, it bled off more speed than that in a standard rate turn.

I'm with Rupert. The OP said he was on AP but didn't mention anything about autothrottles, two separate things.

I'm with Rupert. The OP said he was on AP but didn't mention anything about autothrottles, two separate things.

 

In post#1 he clearly states "I set the N1 speed using autothrottle".

In post#1 he clearly states "I set the N1 speed using autothrottle".

 

I got the impression he was using AT along with AP to get to a stable speed,

and then shut off both and flew manual using the N1 that was last used when

stable speed and using A/T. Then all manual after that with a constant N1.

But maybe I'm cornfused on what he was doing.. :confused:

A more technical answer that hopefully addresses the question as to why the speed didn't return after he rolled out of the turn is that at low IAS and high drag settings the aircraft adopts a more nose-up attitude in level flight which increases drag so that, even at a constant throttle or N1 setting, IAS will not increase - thrust:drag relationship is NOT the same as trim:drag which can be regarded as a constant, all other things being equal.

Just different numbers fit the same equation(s)

Mathmatics wins again! :D

And yes, "The Equation", as well as all aerodynamics, apply to all aircraft.

Except maybe choppers. They're like bumble bees, they can't really fly, they just never read that book...

However I will say I was surprised. It's been 50 years since I've been in the right seat of a Marine R-4. But if I recall correctly, it bled off more speed than that in a standard rate turn.

And yes, the DC-3 bleeds speed pretty fast, but you also have to make sure you rudder properly. It has a huge rudder, and is sorta twitchy about it.

The DCAirlines DC-3NH and the Manfred Jahn C-47V2 have, from what I can tell, pretty well done FDEs. If you want to try a DC-3/C-47 they are both a big improvement over the default.

Just a little heads-up :D

Pat☺

I got the impression he was using AT along with AP to get to a stable speed,

and then shut off both and flew manual using the N1 that was last used when

stable speed and using A/T. Then all manual after that with a constant N1.

But maybe I'm cornfused on what he was doing.. :confused:

 

You are correct. I was using AT and AP to get a read on pitch and power for manual flying. I then turned AT and AP off made a turn then flew straight and level. I just wanted to compare things like altitude to see how well I made the turn. I'm not a very good manual pilot in jets, but I keep trying.

And yes, the DC-3 bleeds speed pretty fast, but you also have to make sure you rudder properly. It has a huge rudder, and is sorta twitchy about it.

 

 

Pat☺

 

Good analogy! I've known people with huge rudders that are sorta twitchy about it too!

 

Almost all tail-draggers really are much happier when you keep the ball centered. However skidding in the sky is never a good thing. That's why I always encourage people to practice with a tail-dragger at least occasionally. Best stick and rudder practice I know of.

 

And thanks for the download ideas. I'm probably less happy with the default DC-3 than any of the default fixed wing birds I've tried.

Good analogy! I've known people with huge rudders that are sorta twitchy about it too!

I aint sayin a word about the Kardashians, or John Holmes... :D

 

And thanks for the download ideas. I'm probably less happy with the default DC-3 than any of the default fixed wing birds I've tried.

My pleasure. I've been flying the DC-3NH from DCA recently for the World Rally, and while it's taking me some time to get back to stick AND rudder, it's a lot of fun, once I started getting the hang of it.

I've been flying the FSDT F/A-18C v15.6 a lot of late, and due to the design of the airframe, it's normally flown "feet on the floor" (direct quote from the NATOPS!). No rudder needed for normal maneuvering, although the rudder is still used for some maneuvers most other types of planes can't do. Think "pirouette maneuver".This has made the sudden jump into the DC-3 a real adventure for me, trust me! Big, slow, lumbering, and with a sensitivity to it's rudder inputs, and a lack of engine power (whaddya mean there's no afterburners????). Definately taking a lot of practice.

 

But anyway...

Pat☺

I aint sayin a word about the Kardashians, or John Holmes... :D

 

 

My pleasure. I've been flying the DC-3NH from DCA recently for the World Rally, and while it's taking me some time to get back to stick AND rudder, it's a lot of fun, once I started getting the hang of it.

I've been flying the FSDT F/A-18C v15.6 a lot of late, and due to the design of the airframe, it's normally flown "feet on the floor" (direct quote from the NATOPS!). No rudder needed for normal maneuvering, although the rudder is still used for some maneuvers most other types of planes can't do. Think "pirouette maneuver".This has made the sudden jump into the DC-3 a real adventure for me, trust me! Big, slow, lumbering, and with a sensitivity to it's rudder inputs, and a lack of engine power (whaddya mean there's no afterburners????). Definately taking a lot of practice.

 

But anyway...

Pat☺

 

Pat,

 

The real secret to success taxiing a tail dragger is to not have heavy feet! Just tap tap tap at the rudder. If you hold it down, the action will speed up very quickly.

 

In fact, with that big rudder in the air, you want to again be careful to have light feet. You'll never maintain any speed otherwise.

 

Oh, if your plane has a tail wheel lock, unlock it to taxi!

Pat,

 

The real secret to success taxiing a tail dragger is to not have heavy feet! Just tap tap tap at the rudder. If you hold it down, the action will speed up very quickly.

 

In fact, with that big rudder in the air, you want to again be careful to have light feet. You'll never maintain any speed otherwise.

 

Oh, if your plane has a tail wheel lock, unlock it to taxi!

Thanks for the info, Rupert! Every ittle detail helps me a lot.

Believe it or not, taxiing isn't really any trouble. Sometimes I wish I had a split throttle quadrant for my system, but hey, wish in one hand...

No, it's remembering to keep my turns coordinated with the rudder that often trips me up, but I'm getting better and better with every turn. Since I originally learned in gliders, I am used to massive rudders :D I just need to get BACK to those days, mentally.

How do you get to Broadway? yeah.

Anyway, Time to work hard on WR2015 Flight #3 before I miss the dead-line to file a PIREP.

Have a great flight all, and even better holidays!

Pat☺