Climb rate. (1 Viewer)

Shortround6 said:

but since the drag goes up with the square of the speed trying to climb while going fast in the forward direction doesn't work well either.

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Lift also goes up with the square of the speed so increasing speed also provides as significant an increase in climb as it does drag. It seems to be a battle. If we take two aircraft with identical wings and therefore identical Cl and area, both have identical weight, and both have identical normal rated thrust, but airplane A is much dirtier than Aircraft B, and compare these two aircraft we find that Aircraft B can maintain a higher speed than aircraft A with the same power and same angle of attack. It is this increased of airspeed that translates into a faster horizontal velocity and more lift thus faster climb (vertical velocity) or as flyboyJ would say Vy and Vx which is the results of excess power of airplane B as SR6 stated. That's what I think!

Basically, comparing climb performance based only on power, weight, and wing area leaves significant data out.

Shortround6 said:

Fastest for how long (or high)

Some planes could climb very well at sea level and for 1-3 minutes and then tended to "flame out".

Others started a bit slower but could maintain a good climb for a number of minutes.

A select few could both climb well at sea level and keep climbing well 5-10 minutes later.

Do you want the fastest in FPM ( or meters per sec) at sea level or fastest to 10,000ft ( 3000 meters ) or 20,000ft (6,000) meters or???????

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im sure because of variables that militaries had some standard test means, but being a former top fuel and funny car racer . It seems to me that preparing for combat would be the purpose. Here. Say that each plane would be prepped for combat at the target altitude. Combat munitions, fuel and what ever was needed. Planes to be only prop planes for this test. We arrange them on a nice runway far enough apart so they won't have accidents.. electronic beam across the runway, picked up the tires. Just like drag racing.. to complicate a little altimeters must be calibrated equally. must Be the same model. . Modify the dash hole as required but system must be the same. Stop determined by altitude . Electronically timed. We want to time each plane to compare so each breaks it's own starting beam. We can drag race later. For now just who is fastest on record.

ready….. set. GREEN. Go! Kamikazes are coming. Elapsed time wins and is number one qualifier for the real race.

byron

There is a very good basic formula for rate of climb. Not infallible, but pretty good for an estimate.

RC = 33000 * (PA - PR) / W, where PA = power available (hp). PR = power required for level flight, W = Weight (pounds). RC = rate of climb (feet per minute).

Take a Hawker Sea Fury. Normal specs for a Sea Fury FB.11 show: Gross Weight = 12,350 lbs. HP at sea level = 2,480. Known initial rate of climb = 4,320 fpm.

Solving using the formula allows us to solve for power required: PR = 863.2727 hp.

So, if we let the weight drop down to, say, 10,400 pounds, we can estimate a rate of climb at 5,130 fpm. At that weight, there isn't much fuel or ammunition left, so the sparkling performance won't last for long or do much good, other than to support the lifestyle and feeling of power of the pilot.

The Vought F4U-4 Corsair has almost the same specs. Gross weight as a fighter = 12,405 pounds. HP at sea level = 2,400. Known initial climb rate = 4,360 fpm.

Solving for power required gives = 761.0364 hp.

Again, if we let the weight drop to, say, 10,400 pounds, we expect a rate of climb of about 5,200 fpm. These two planes perform almost exactly the same, with very similar expected climb at very light weights.

Both planes only have these climb rates at war emergency power (2,400 hp or so), with the throttle breaking through the wire stop. At normal military power (1,500 hp or so), both are considerably less sprightly in climb. For both, I'd expect a cruise-climb at 2,000 - 2,200 fpm for most operations. Max rate of climb would be in the heat of combat, not normal flying.

looking at my reply above, I apologize for missing the point!

The main reason there is so much disparity among reports of things like top speed and rate of climb is the almost complete lack of test data. It makes a difference, sometimes a BIG difference, what the test weight was, whether or not WER was used for the climb power stetting, and whether or not there were racks / rails fitted to the wings. It CAN make a difference whether or not the cowl flaps were open or shut. Most of the time, when we see an initial rate of climb quoted, the basic aircraft data for the test are not included in the text, and it makes a huge difference.

Most WWII fighters had three weights reported; empty weight, gross weight, and maximum takeoff weight. Standard aircraft characteristics are generally given at gross weight and military power. Sometimes they report using WER, but you have to check to find out. Whenever you see very high rates of climb, it is generally clean, no racks, WER and minimal weight. Think an empty airplane with maybe 1/3 fuel and half or no ammunition. That is NOT a good position for the pilot to be in if he is 200 miles from base and in a fight, but it makes the airplane look really good in a brief performance report. WER consumes fuel at a prodigious rate and low fuel is not what you need unless you are over your own home runway.

By way of example, retired AVG pilot Johnny Allison paid a visit to Joe Yancey's hangar while I was working there and talked about demonstrating the P-40 for Claire Chenault. He mentioned using 75" MAP for the demonstration and flying with half fuel, no ammunition, and no survival kit / extra anything inside. At the time, the maximum approved MAP was 47". Naturally, the P-40 put on a sparkling display. But most of the time, it didn't perform like that because it was being flown within approved limits and was loaded with fuel, ammunition and normal loadout items.

bentwings said:

im sure because of variables that militaries had some standard test means, but being a former top fuel and funny car racer . It seems to me that preparing for combat would be the purpose. Here. Say that each plane would be prepped for combat at the target altitude. Combat munitions, fuel and what ever was needed. Planes to be only prop planes for this test. We arrange them on a nice runway far enough apart so they won't have accidents.. electronic beam across the runway, picked up the tires. Just like drag racing.. to complicate a little altimeters must be calibrated equally. must Be the same model. . Modify the dash hole as required but system must be the same. Stop determined by altitude . Electronically timed. We want to time each plane to compare so each breaks it's own starting beam. We can drag race later. For now just who is fastest on record.

ready….. set. GREEN. Go! Kamikazes are coming. Elapsed time wins and is number one qualifier for the real race.

byron

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Another test would be to ring up a squadron at random and tell them an enemy bomber is circling at 18,000ft one mile to the south of their airfield. Stop the clock when 12 aircraft have formed up on the decoy. The difference between best and worst in WW2 was measured in fractions of an hour not minutes and seconds.

Almost all of the surviving WWII fighters still flying are privately owned. The likelihood of the owners letting someone thrash their airplanes nd VERY expensive engines for such a test at WER is shockingly close to zero. There are a dearth of pilots qualified to thrash these airplanes as you describe and do it safely since most have never run gasoline higher than 100-Octane Low-Lead. Nobody will let you change is or her altimeter to make them all standard. You'd have to fit auxiliary altimeters. Many lightweight unit are available.

Alas, we pretty much have to reply on test conducted during WWII or while they were still in Military service.