Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: oboe on March 11, 2003, 12:01:11 PM
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I can't seem to deadstick a landing in the A6M2. Once I lose engine power, it seems to drop like a brick. How could such a light airplane have such a poor glide ratio? Is it from drag? I thought the Zeke is a fairly clean a/c for a radial-engined airplane. The Ki.61 is a heavier aircraft but I found I can glide a long, long time in that plane.
Alos, is their a problem with the A6M2's damage model. Several times I've been hit and noticed a fuel leak, but my damage console indicates no damage. Anybody else notice this?
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Oboe,
On the glide ratio issue I haven't tested the A6M2/5 but it should glide well. What speed are you starting your glide from? I find that the best glide ratio is usally achieved at the same speed used for best climb. In the Zeke that is about 135MPH I believe. The aspect ratio is quite high in that bird and that usually means a good glide ratio.
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My experience is the same as Oboe's. The A6M is the hardest aircraft for me to deadstick a landing with.
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Yep that plane cannot glide worth a damn, Bf109 for example can glide much much better no matter what... This is odd because the zero is very light, has a high aspect ratio wing, and is very clean aerodynamically.
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Prop drag maybe? reduce RPMs
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It makes no difference about rpm the zeke drops like a brick. reducing rpms does allow to glide better but its still a brick. Its very nose heavy even when landing under power. Its very easy to ding your prop.
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Same with the Typhoon and Tempest. I'd bet the problem is that all the other planes glide too well.
ra
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F4UDOA - if you have a standard glide test to perform, I'd be interested to see the results of the A6Ms.
I don't any wingloading figures for aircraft, but would certainly expect the A6M2 to be one of the lightest loaded planes of all in the set. I would think that would translate to outstanding glide characteristics.
Glad to see others had noticed this too. I thought I'd lost it during my absence...
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I find when i drop rpm on the typh it glides quite well...
SKurj
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Glide ratio has nothing to do with wingloading or weight. Glide ratio = Lift/Drag ratio.
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Why does a bf109g6 then glide much better than a zero?
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Glide ratio = Lift/Drag ratio
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Oboe,
I don't really have a standard test but I can tell you in my test I climb as high as 20K throttle back and try to find a speed in which you can maintain a steady decent rate while maintaining airspeed.
This was much more difficult than I aniticipated.
I found a few things.
1. I could maintain approximately 85MPH while decending at 3K per minute. This weird because I was at a steep dive angle with the stall buzzer blaring the whole time. It seemed as if I was parachuting not diving. Even at a high dive angle I could not accelerate. Very strange.
2. I could maintain a 114MPH glide for a while at a 4K decent rate which again is strange because again it was a very sharp angle and it felt like I should have been accelerating. It had the feel of dragging something behind me like an airbrake or something.
3. I seemed to have the best sensation of gliding at about 160MPH to 140MPH TAS. However at this speed my decent was in excess of 4K per minute which I believe is too high and is more like falling than gliding.
However the biggest indication of something amiss was during the climb. My best climb speed at sea level when viewed on the digital viewer was 150MPH TAS at sea level increasing to 200MPH TAS at 20K. The best climb speed for the A6M5 according to TAIC data is 121MPH which mean the A6M2 should be the same if not less. Generally the best climb speed is the speed in which the wing generates the most lift as well as have the best thrust to drag ratio. Based on that the best glide is usually close to the best climb and our climb speed is way to high.
It seems our A6M2 has an unusual lift/drag curve which may prevent it from gliding as well as it should at the right speed IMHO.
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I got a 1k/min descent at 100mph in A6M2, full fuel, 2000feet cut engine.
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Some food for thought:
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- What do you expect the glide ratio of a A6M2 to be? You should have this as a starting point before evaluating the FM.
- Best glide performance / ratio is determined by best L/D ratio. L/D max for a given airframe is always the same regardless of a/c weight. This really throws folks- another one of those non-intuitive aerodynamic things. I'll spare the mathematical explanation of this.
- Best-rate-of climb occurs "to the right" or at higher velocity than occurs at the best L/D ratio for prop planes. This is because the difference between power-available power-required is not at it's maximum at the lowest point of a/c drag. That being said velocity for best rate-of-climb is a good data point to get you in the ballpark for best glide velocity.
- On glide tests here is a typical flight test method: use a constant velocity glide test repeated across a range of different velocities to determine your best glide velocity. Time how long it takes to cross a set altitude band (500 - 1000 ft is enough) at a given constant velocity. Multiply the velocity by the time to descend across the altitude band. Do this for the range of velocities you're interested in. Plot the time x velocity product vs. velocity. You'll get a parabolic curve. The peak of the parabolic curve will give you your best glide velocity. You can use the .set speed and alt-x functions to have your a/c maintain a constant velocity. Also your airspeed should be stabilized at constant velocity when you get your data so give yourself some altitude in descent to let your airspeed settle before you cross your test alt band.
Tango, XO
412th FS Braunco Mustangs
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Dtango,
Don't you think it's odd that the A6M2's best climb speed is so high? 150MPH is about 30MPH over what it should be.
What does that say if anything??
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I have no flight test data outside of AH besides what you've quoted on the A6M2 velocity for best-rate-of-climb so can't comment on the differences. HTC is pretty thorough in their research and engineering.
By the way lift is not a factor in sustained climb performance.
Back to the topic of glide performance, the place to start is to determine what the expected glide ratio of the A6M2 is then compare.
Tango, XO
412th FS Braunco Mustangs
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Using the .set speed command/alt-x at ranges from 150 down to 100 (can't use it below that) I got descent rates ranging from 4800 fpm to 3260 fpm. This was an A6M2, 50% fuel, starting at 4000' and measuring the time it takes to pass from 3000' to 2000'.
When I plotted time x velocity vs velocity, I did see a peak at around 130 mph, but I can't say the plot resembled a parabola...
Still, 130 mph correlated to around a 4100 fpm descent. I would've expected a number closer to what davidpt40 produced, but I can't come anywhere near achieving that.
As far as glide ratio being the lift/drag ratio and independent of a/c weight, isn't the lift vector a relative force, detemined by the upward force produced by the wing at a given speed/altitude minus the downward force of gravity, which is basically the weight of the a/c? So while glide ratio may be lift/drag, the lift component is partially determined by the weight of the aircraft?
Thanks!
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Oboe did you plot glide ratio? Glide ratio is the ratio of horizontal speed to vertical speed.
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I'm no aeronautical engineer, but I noticed with the inclusion of the A6M5b we have that they glide very poorly.
Why? I have not a clue.
I've been at alt (or what I call alt....20K+) and noticed that the Zeroes glide distance is far less than say, a P-47. Like others have said, you have to really stick the nose down to keep your speed constant.
I've had a P-47D-30 at 20K in the NDIsles terrain, ran out of fuel while rtb'ing, and I was able to glide from half a sector S of A45 all the way to A47. Actually, it was a bear to get the thing slowed down enough to stick her on the runway when I got there.
Seems the Zeroes have too much drag. I'm not sure how "clean" they actually were in RL. But from everything I have ever read about them, the AH versions pale in comparison to the RL planes.
Example: Last CT setup, I took an A6M2 up to 25K. Why? Cause the Allied guys were staying up that high, and I hate fighting uphill.
Anyway........EVERYTHING I have ever read about the P-40's stated that they were a dog above about 15K....some sources say 12K was really the max alt you wanted to see in one, but I digress............RL accounts indicated that upstairs where I was flying, 20K plus, suited the Zero better than the P-40. Not so, at least from my experience. The P-40's were leaving me in the dust. Maybe it was my crappy flying, but accounts from Allied pilots who were "there" said that being caught at those alts by a Zero was suicidal. The P-40 was just wheezing along while the Zeroes were still going strong.
IMO, the Zeroes in AH have too much drag. Furring at low alts against even F4F's I found myself stalling in turnfights, while my opponents seemed to stay in control. The A6M's seem to bleed E even worse than the much heavier Jugs do, and that is saying a lot.
Maybe Pyro could look into some of this. I confess I do not have documentation, at least not from he might call a reliable source. All I have are the normal books and reference sources everyone else has.
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Originally posted by ra
Same with the Typhoon and Tempest. I'd bet the problem is that all the other planes glide too well.
ra
The typhoon and tempest are extremely heavy... it's my understanding that they're armoured fairly well, and I know for a fact they had huge engines. Their glide ratios seem ok to me.
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oboe:
Did you reduce prop pitch by reducing RPM to lower windmilling prop drag? I did a real quick test of the the A6M2 25% fuel glide at 140 mph at low alt resulting in about a 1600 fpm descent.
Lift=Weight in level flight. Whatever the weight of your a/c, that's the lift you need to produce to stay in level flight. It get's a little more tricky in a glide since lift and weight are no longer vectors opposing each other by 180 degrees.
L/D is a ratio. The ratio remains constant in a glide even with different aircraft weights involved. Yes lift varies with weight. However the L/D ratio remains the same because drag changes as well so you end up with the same L/Dmax ratio. In otherwords the lift and drag change because of the different weights but the ratio remains the same. I know it sounds weird but that's how the math works out. If you have two of the same aircraft but at different weights they will have different velocities for best glide (lighter = slower best glide speed) but will have the same glide ratio.
Another way to think of it is that for best glide the angle of attack is always constant no matter the weight of the a/c because that's the aoa that produces the most efficient L/D ratio for the a/c.
Tango, XO
412th FS Braunco Mustangs
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Originally posted by F4UDOA
Don't you think it's odd that the A6M2's best climb speed is so high? 150MPH is about 30MPH over what it should be.
What does that say if anything??
The Zero in AH does enjoy it's best rate of climb if you manually set speed to 122, rather than going with the default autoclimb setting. The difference is slight, but consistent, and most pronounced over 15k.
Vladd