Aces High Bulletin Board
Help and Support Forums => Help and Training => Topic started by: pembquist on March 04, 2011, 02:21:05 PM
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I have Avfuel Deficit Disorder and can someone tell me how find best glide? I thought it would be close to best rate of climb which I thought was the default speed when you hit alt x. Gliding the spit 8 i thought I would cover more ground than I do.
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That's a good question. I have bad luck with the radiator in the Dora sometimes and have to glide most of the way home. If you've got enough altitude I would recommend just using the Shift+X autopilot with our nose just a little bit below the horizon.
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The lift curve is kind of flat before it drops off so it's good to err on the fast side. I like to glide around 200 indicated.
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first off when gliding you should wind your rpms all the way down, reduces drag alot. I glide home alot and do it by making sure that I'm level and have as much speed as possible before the engine quits (after a WEP climb at best climb rate), then setting the descent rate to 500-1000fpm. I figure you want to be as fast as possible to start with because theres more chance of being bounced further out from your base.
does gliding all the way at best climb speed maximise the ground you cover? I'm not sure about that :headscratch:
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Best climb speed is too slow. Also your max time aloft speed does not cover as much ground as best glide speed. Good point about RPMs.
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I suggest:
1. Reduce RPM at minimum - but take care to have no roll;
2. Reduce manifold a bit - now you will suffer roll a bit;
3. Do not exceed 0 climb rate.
:salute
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I believe Pyro or Skuzzy chimed in once and said "about 10mph slower than best climb"...
Just be sure to reduce RPM like mentioned above.
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DamnedRen ( <AH BBS username ) or Ren did some good research on this a few several years ago when he was still an AH Trainer...if you do a search on the boards and only do an advanced search using only the Aces High Help & Training Forum and use Glide Speed and Ren you might find it.....
I'll see if I can dig it up for you this evening, if noone has found it by then.....
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I believe he was more interested in distance covered than least amount of descent. That's another subject altogether, and an interesting one. I personally use auto climb default while descending unless I need a bit less than the default speed (i.e. scraping the ground a the last second)
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I did some testing with a P-47M a while back. What I found was that best glide speed was faster than the default alt-x speed for the Jug-M. Prop drag can have a considerable impact on the distance you can cover while you glide.
The graph shows best glide speed with and without the prop feathered (representing an out-of-fuel condition versus engine damaged and out condition).
Aircraft was at 14,000 lbs and at 5,000 feet MSL...
(http://i125.photobucket.com/albums/p61/stonewall74/PropDrag.png)
For glide speed, lower is better...
I can refer to you to the testing methodology I did, but its pretty laborious. Just off-hand for MA use, I'd take the default alt-x speed of the plane and add 10-15%.
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Why did you use TAS instead of IAS?
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Don't know...I'd have to go back and look at my numbers/notes from the test. There was a reason though. That being said, I suppose the conversion can be done using standard conditions
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Why did you use TAS instead of IAS?
Looking at my notes:
I used TAS in order to determine the speed at which the most horizontal distance is covered, since ground speed (assuming no wind in AH) is = to TAS. Looks like the IAS was 175 for the windmilling condition and 180 for the stopped condition.
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Here is the write-up from Ren I had saved it awhile back.
There are 3 standard auto pilot settings in AH2. Auto Level, Auto Speed and Auto Angle. you can test
them using x, alt-x and as you said ctrl-x. One thing about the auto pilots is if your stick needs
calibration it might not hold the auto pilot you engaged.
Auto level is level flight. Self explanatory.
Auto Speed sets the climb rate in MPH. For example, a Yak will go from take off to almost 16,000 at
230 mph. Not bad if your wanting to grab while covering lots of distance, and grabbing a drink. To set
it you merely bring up the text buffer (/ key), type in .speed 230 and hit enter.
Auto Angle is a little different and you've touched on a nifty fact about it. Yes, you might point the nose
skyward and hit ctrl-x and the plane will climb until she runs out of airspeed then her nose will slowly
drop a required amount to maintain as close to the original nose up configuration as she can muster. At
that point she may be very close to the edge of a stall. If you click out of the
auto angle mode she just might fall off on you. Another nice thing is you can trim to a given speed then
hit auto angle and she'll stay there. This is helpful when you find you are just about out of gas but you
may be able to convert some altitude to distance.
Many of the planes will glide, engine off, at 120 mph in a 1,000 fpm descent. That's 2 miles for every
1000 ft of lost altitude. If you're trying to make a field that is 12 miles away and you have 7k altitude
you will glide home safely. Just trim the plane nose low to around 500 descent and hit auto angle. She
will slowly nose down to around 1k fpm descent
Another sneaky fact about fuel burns to get you home. Hit auto level and pull all the power off the
plane. Throttle back rpm and manifold. The plane will begin to slow. Eventually you will begin to there
the stall warning buzzer. Bring up your E6B and begin adding just enough power to maintain level
flight, no more. Now take a look at your E6B. You will have gone from 3 miles of gas left to 100 miles.
And you maintaining level flight! Try it. See what distance your favorite ride will give you when you
just finished a fight and looked at the ole gas gauge. You may get home with ease.
I think
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See This Thread: http://bbs.hitechcreations.com/smf/index.php/topic,308176.0.html (http://bbs.hitechcreations.com/smf/index.php/topic,308176.0.html) (or at least the first post)
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Keep in mind that a heavier aircraft will fly faster for a given glide ratio but will cover the same distance.
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See This Thread: http://bbs.hitechcreations.com/smf/index.php/topic,308176.0.html (http://bbs.hitechcreations.com/smf/index.php/topic,308176.0.html) (or at least the first post)
MachFly, your methodology in that set of tests has given you results that I suspect are incorrect.
Try using the glide test methodology described in this series of web pages: http://www.avweb.com/news/airman/182410-1.html
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MachFly, your methodology in that set of tests has given you results that I suspect are incorrect.
Try using the glide test methodology described in this series of web pages: http://www.avweb.com/news/airman/182410-1.html
I read the info on the link you posted and I can't find anything that contradicts my test. Basically it says to test it changing your airspeed not decent rate which is exactly what I did.
Maybe I missed it, could you show me where exactly it says that.
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lil bump here because I noticed something relevant in the N Jug manual:
The best rate of climb is obtained at 155 mph
TIP: If you should ever have to make a
forced landing in which covering the maximum
horizontal distance is essential (such as engine
failure over water and you want to get as close
to shore as possible) , glide at 230 mph with
wheels and flaps up.
:headscratch:
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lil bump here because I noticed something relevant in the N Jug manual:
:headscratch:
Thing I noticed about best climb rate is that it's better to look at it as a range of speeds rather than one particular speed. The game's Autopilot Speed defaults to 175 for planes like the P-51D (which I assume is the optimum speed for climbing), but you can get a similar rate of climb with a difference of no more than 100fpm from 190 all the way down to 155. I remember testing a P-47M and all I remember is the data was almost identical, you get into your best climb performance once you pass 155 and you leave that perfomance window somewhere around 200.
It's my assumption that the manual was saying that you can start doing some serious climbing once you get your airspeed to 155.
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Well as a sailplane pilot we like to call this the best l/d (lift over drag) so for my sailplane my best l/d speed is 55 mph which you dont want to do in a spit 8 :lol
So maximize lift and minimize drag.
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Thing I noticed about best climb rate is that it's better to look at it as a range of speeds rather than one particular speed.
You're absolutely correct. All of your "best" speeds change with weight. The heavier the aircraft is, the higher the speed needs to be, both for climb and glide. The default alt-x speed is merely the best climb speed for that aircraft in a specific configuration. If someone was willing, it'd be interesting to see what the exact best climb speeds are at different weights.
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I only mentioned it because AH consensus seems to be that best glide speed to cover the most ground = best climb speed (+/-10mph depending on who you talk to.)
this says that its 75mph above best climb speed.
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I only mentioned it because AH consensus seems to be that best glide speed to cover the most ground = best climb speed (+/-10mph depending on who you talk to.)
this says that its 75mph above best climb speed.
Well, I always recommend 10-15% above the default alt-x speed, but Machfly for one, disagrees with me. Certainly +75 mph is above 10-15%. The reality is that the POH lists 155 for "best" climb and lists 230 for "best" glide. Both of the speeds are weight dependent, and, although I haven't tested gross weight best glide speed, I'd expect that the 230 is close to the gross weight best glide (i.e. full fuel and ammo). My testing with the P-47M shown above shows 180-190 range for 25% fuel condition (approx 14,000 lbs). With the P-47N coming in at around 18,000 with full fuel and ammo, 230 seems close to what I'd expect. A couple of factors contribute to these speeds. Typically, manufacturers list Vspeeds at gross weight. I guess this is viewed as "worst case". But, regardless of what configuration they use to develop the listed speeds, those speeds are only valid for that specific configuration. Both best climb and best glide will change with weight, and also with altitude. The higher you fly, the faster your best climb and best glide speeds will be. So, even for us, with the default alt-x speed being a fixed number (like 155mph), if you climb all the way up to 20,000 feet, there will be a period where, in order to absolutely minimize the time to climb, it would behoove you to adjust your speed up to 160-165mph, for example. Or, if you're in a P-47N with max ordnance and fuel (approaching 20,000 lbs) and you want to minimize the time to climb to your desired cruise altitude, you'd probably want to climb faster than whatever the default alt-x speed is. But, for the most part, simply using the default alt-x is the easiest, and probably doesn't penalize you too much if you're flying just above or below optimal. Second, these POHs were developed to be used by the masses for instructional and operational guidelines. For the USAAF to say 230mph is best glide speed, someone decided that, for whatever reason, 230mph would be the best speed to list in the POH. Unfortunately, they don't explain to us what configuration the aircraft was in when they determined that speed.
The bottom line on this is that to be perfectly sure, you flight test both in game. And, I can provide testing methodologies for both to get fairly precise speeds for in-game. However, if you don't want to take the time to do the testing for yourself, just use default alt-x for best climb, and whatever other speed you want for best glide.
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I only mentioned it because AH consensus seems to be that best glide speed to cover the most ground = best climb speed (+/-10mph depending on who you talk to.)
this says that its 75mph above best climb speed.
You have to consider the condition you are gliding in. In AH you can almost feather a prop by setting min RPM, and it makes a major difference. If you have the height, you can pull up and get the prop to stop "windmilling". That is a another major improvement. Bottom line is check it with each aircraft type. The Spit autoclimb(speed) is around 160. It's best glide is around the 130 to 135 mark with the prop on Min RPM or better stopped!
I agree with MachFly on all this.