Increasing aircraft range

[MachFly]

Is it true switching off combat trim helps when gliding?

Combat Trim trims your aircraft for straight & level flight at mill. power, compensating for the torque. When you are gliding you have no torque so you want to trim all your controls straight (besides the elevators, trim those for best glide). If you usually glide on autopilot than don't worry about combat trim. 

[MachFly]

The results on my testing suprised me until last night that I noticed the Burn Multi in the MA is 2 as opposed to 1 off line. So the range will probably be half of what I found out offline. I would imagine it is always 2 in the MA.

Yeah, it's always 2 in MA.

[Blagard]

The best glide for the Spitfire is around 130 (the actual number depends on the model, Spit14 has it at 135). As a matter effect the best glide is lower than auto climb in most airplanes.

Thanks, that's useful to know. I used to fly sailplanes amd hanggliders so I became reasonably accomplished in understanding glide performance dependant on what you are trying to achieve in different conditions.

In AH it's worth getting to know a few basics in performance that can make the difference between just scraping in to base and ditching a few yard short!

[Blagard]

Combat Trim trims your aircraft for straight & level flight at mill. power, compensating for the torque.

Whoa! - That does not sound right - I think combat trim is constantly changing the trim to suit the atitudes you are putting the aircraft in. In game, it affects the amount of stick movement you have to input.

Using the period(dot) trims out current stick deflections for adjustments within the trim range and the othertrims are Auto as in "Auto pilot" for speed(climb), angle and level. And finally there is the manual trims.  Sorry, I digress on my own thread!

[MachFly]

Whoa! - That does not sound right - I think combat trim is constantly changing the trim to suit the atitudes you are putting the aircraft in. In game, it affects the amount of stick movement you have to input.

Using the period(dot) trims out current stick deflections for adjustments within the trim range and the othertrims are Auto as in "Auto pilot" for speed(climb), angle and level. And finally there is the manual trims.  Sorry, I digress on my own thread!

Try flying the airplane at mill power, then cut the throttle. While doing that look at your trim indicators, they will not move and you will feel the airplane really wanting to bank.

Also try flying with flaps while combat trim is on, it just does not work so you have to trim it your self.

[Blagard]

Try flying the airplane at mill power, then cut the throttle. While doing that look at your trim indicators, they will not move and you will feel the airplane really wanting to bank.

True, but now try flying without combat trim on. Put the aircraft in to a steep climb (after getting some steam up) and hold the angle steady using the stick adjustment. Then try putting the aircraft into a steep dive and keep it there with stick adjusment.

Put the combat trim on and do the same. - You will find you don't need anywhere near the same amount of stick input after changing your attitude because the combat trim will move your trims to compensate.

Combat trim is definately not an autopilot and will not compensate for the aircraft wanting to change attitude. It's actually a rather special trim unique to AH and not of the real world (as the world was in WWII). It's more of a playablity aid used in conjuction with the limitations of the virtual world created.

[MachFly]

True, but now try flying without combat trim on. Put the aircraft in to a steep climb (after getting some steam up) and hold the angle steady using the stick adjustment. Then try putting the aircraft into a steep dive and keep it there with stick adjusment.

Put the combat trim on and do the same. - You will find you don't need anywhere near the same amount of stick input after changing your attitude because the combat trim will move your trims to compensate.

Combat trim is definately not an autopilot and will not compensate for the aircraft wanting to change attitude. It's actually a rather special trim unique to AH and not of the real world (as the world was in WWII). It's more of a playablity aid used in conjuction with the limitations of the virtual world created.

OK, my definition of combat trim was incorrect but my original point (using combat trim in glide) is right.  


I do not understand why would it compensate for the pitch, but not compensate for the power & flaps. I guess we should just call it "Various Pitch at Military Power in Clean Configuration Trim", shortened to "VPMPCCT".  

[Blagard]

Also try flying with flaps while combat trim is on, it just does not work so you have to trim it your self.

This is a different problem because flaps have different effects on different aircraft. I suspect combat trim is optimised for use without flaps, so you are going to have to compensate for the difference manually. It does not help if you loose a wing tip either, again you have to manually trim that out.
For what it is intended for, it does OK - Just remember it is a game aid not a real world equivalent trim.

OK, my definition of combat trim was incorrect but my original point (using combat trim in glide) is right.

I was not debating that point. but combat trim is of very little use in the glide because you do not change attitude much if at all. The poster wondered if it had any effect on the glide and the practical answer is no it doesn't.

[MachFly]

This is a different problem because flaps have different effects on different aircraft. I suspect combat trim is optimised for use without flaps, so you are going to have to compensate for the difference manually. It does not help if you loose a wing tip either, again you have to manually trim that out.
For what it is intended for, it does OK - Just remember it is a game aid not a real world equivalent trim.

Loosing a wing tip is not normal, using flaps is normal. If it was meant to be used in combat than it should compensate for flaps as well.

I guess your right, it's "OK". I personally don't really use combat trim (only in high speed fights) so I have my trim controls at my fingertips while flying.

[Blagard]

Loosing a wing tip is not normal, using flaps is normal. If it was meant to be used in combat than it should compensate for flaps as well.

Ah!  - A valid point - I agree that as a normal control surface used in combat by some aircraft it should compensate. I think this is just a question of how complicated the coding gets when you introduce that factor! - So it would seem they have not done so.
Thanks for the debate though   it is always a good change to have sensible one on this forum.

[Stoney]

As a matter effect the best glide is lower than auto climb in most airplanes.

No, hardly ever will this be the case.  Best glide speed will almost always be higher than your best climb rate speed.  I won't get into the actual mechanics of it unless someone wants it, but a couple of points.  First, best glide speed changes with weight and altitude.  Second, for a rough estimate of best glide speed (without testing it), add 10-15% to your Alt-X climb speed.  If you're heavier (say a shot up engine with a good amount of fuel and ammo remaining) go for the 15% figure.  If you're light (ran out of gas and no ammo) go for the 10% figure.  This will get you closer to the actual.  Third, the easiest way to glide home, is to use the [.setspeed xxx] command.  If your Alt-X climb speed is 160, use the .setspeed 175 (adding 10% to your best climb speed) command line in the text box, and then hit Alt-X.  The game will trim the plane for 175 mph IAS, and it will keep you from scrubbing off distance from manual flying.  These are not exact, and may not be the best glide speed, but they're close approximations.  If you really want to know your favorite ride's best glide speeds, you'll have to do some testing in-game.

Now, to increase your overall range, you need to (1) only climb as high as you absolutely need to, and (2) pull power and RPM back below the "cruise" settings in the E6B.  If you have a long distance to travel, the best fuel economy occurs if you fly at that minimum power setting, as low as you can, and then at some point before you enter the combat area, climb to your desired altitude at full power, using your normal alt-x speed.  Once you get to your desired altitude, level off and accelerate to your chosen cruise/loiter speed, then pull power and rpm back to some combination that will give you the absolute minimum fuel consumption necessary to maintain that speed and altitude.  Once you're ready to RTB, descend back to the deck at idle, using your best glide speed, and then level off at some safe altitude above the terrain, and resume that min-power setting on your throttle/rpm.  Now, some of this may not be practical from a tactical standpoint, and it will either require some testing for you to figure out your best power settings, or you can look them up in a POH for your favorite aircraft.  You'll want to look for something like "Minimum Specific Fuel Consumption" on the engine charts for that aircraft, such as this one for the earlier P-47s:



I personally use the 1800 rpm / 32" MP setting in all of the P-47s in-game at most altitudes.  These numbers won't be exact for each model, since they used different versions of the R-2800 engine, but they're close enough for the girls I date.  I can usually fly 3 or sometimes 4 sectors home on 25% fuel in a P-47 using this setting.  Most of the American ride's have charts like this you can find--I don't know about the non-American rides, as some lack a lot of documentation online.  But, hopefully you get the idea.  Also, if you want to take the time, you can do some testing on or off-line with a stop watch, using different power/rpm settings and timing your plane over a set distance to see what settings give you the best fuel economy.  Remember though, that fuel economy is a function of minimum fuel consumption over a timed distance.  Simply setting for minimum consumption that keeps you airborne will only give you your maximum endurance setting, meaning that you'll maximize your time in the air, but not the range.

There's a lot of aerodynamic theory involved with this stuff, which if you're interested, we can get into, but:

TL;DR:  Best glide speed is always higher than your best climb speed by about 10-15% and maximum fuel economy is achieved by flying low and slow to and from the target area.  This is how Lindbergh got across the Atlantic.

[Blagard]

Stoney, Very interesting data, but on this occassion I agree with MachFly. It seems to work his way around in AH which is what we are looking at.

I did a test using a Spit 16 at 130mph, 160mph(default) and 180mph. with glides from 2000
130 was the longest then 160 and finally 180 the shortest.

From 2000 feet they would all just about make the same distance to land due to the additional "float" the higher speed glides give at the end of the flight. All were with prop on min RPM.

I think I might try them all with the same initial energy state of 180MPH at 2000 and capture the landing on screen shots rather than glide to impact!

Edit: I have just done it again with the same energy state at the beginning. The slower speed 130 covers the greatest distance. So the answer is convert your speed to altitude with a gentle climb and then glide at the slower speed. Perhaps the P47's in AH behave differently. That I have not checked. 

[Stoney]

Stoney, Very interesting data, but on this occassion I agree with MachFly. It seems to work his way around in AH which is what we are looking at.

I did a test using a Spit 16 at 130mph, 160mph(default) and 180mph. with glides from 2000
130 was the longest then 160 and finally 180 the shortest.

From 2000 feet they would all just about make the same distance to land due to the additional "float" the higher speed glides give at the end of the flight. All were with prop on min RPM.

I think I might try them all with the same initial energy state of 180MPH at 2000 and capture the landing on screen shots rather than glide to impact!

Edit: I have just done it again with the same energy state at the beginning. The slower speed 130 covers the greatest distance. So the answer is convert your speed to altitude with a gentle climb and then glide at the slower speed. Perhaps the P47's in AH behave differently. That I have not checked.  

Never climb to reach the slower speed--you will never recover the energy you use to increase your altitude.  Go auto-level and wait for the plane to decelerate to the best glide speed, then begin to descend.  

So what were the exact distances covered?  I don't know that the alt-x speed for the Spitfire is Vy, but it is pretty close for the U.S. rides.  What is almost always true is that Vglide is greater than Vy.  

What I'd suggest is to test the glide speed this way:

1.  Level off at 6,000 feet.  Set fuel burn to 0.  Use .setspeed xxx to set the glide speed you want to test.  Once stabilized at 6,000 feet, with as little deceleration as you can manage, hit alt-x and reduce power to idle.  For the first 1,000 feet, check your gauges to make sure the rate of descent and speed are stable, and get ready with the stopwatch.  If your rate of descent and speed are stable, start the clock as you pass through 5,000 feet.  Stop the clock as you arrive at 4,000 feet, and note the number of seconds it took for you to glide 1,000 feet.  Make notes of your tested speed and the time.  Write down both the TAS and IAS of the tested speed at that altitude, or you can do the conversions from IAS later.

2.  Repeat step 1 at least 2-3 times for each speed tested in order to make sure your data is consistent.  I used 5mph intervals for my P-47 testing, starting at 20 mph slower than alt-x speed and going all the way up to about 40 mph above.  Once you have consistent data for each speed tested, we can start to crunch the numbers.

3.  You need to do a couple of things here.  First, convert your IAS (or the speeds you used for the .setspeed xxx command) into TAS (because in AH2, TAS = Ground Speed unless winds are active) by using a online conversion website, or from your notes.  If using an online conversion, use the TAS at 4500 feet, standard conditions (59 degrees F and 29.92 pressure).  Now, using the time it took to descend 1,000 feet, and your converted speeds, you can determine how far horizontally you flew in feet, over the course of that descent.  Chart the result, and look for where the DeltaTime X Vtas is maximized, and that's your best glide speed, for that weight.  It should look something like this:

[Blagard]

Never climb to reach the slower speed--you will never recover the energy you use to increase your altitude.

So what were the exact distances covered?

I figured to store the excess energy in altitude because I get away from the higher drag quicker. I most certainly do recover the energy from altitude, thats one very fundamental ACM issue but note you may mean I don't recover all the energy used.

I did not measure overall distance as such. I compared the end point of each whilst using the same start point.

Method was to climb to 2000, use .speed 180 command (btw it's not .setspeed) and engage auto speed(climb). Use throttle to fine tune altitude and maintain 2000. On reaching a set point (the Radar tower in my case), cut engine and drop RPM to min. You are on auto pilot fixed at a 180 glide all the way down.

For slower speeds you loose some energy because of the climb. At the set start point you have to be quick after the engine cut and Min RPM to hit level auto trim and then type in the command .speed 130 (or 160) and hit auto speed (climb) again.

In all cases the auto pilot is keeping you straight. At 100 feet I came out of auto pilot to skim the ground as far as possible at less than 50 feet alt until you can stay up no longer. (Landing gear up). I used F3 and a vertical look down for passing over the radar tower start point.

[W7LPNRICK]

30 inches

yup