I have a document called "Fw 190A-8 Aircraft Handbook" that GATT gave me (thanks Bud!) which is a translation of a Focke Wulf document. At the end of it are Range & Endurance Calculations for the aircraft in several load conditions.
I decided to look at one of these cases. Fw 190A-8 with 4 x MG 151/20, 2 x MG 131, full ammo load, no external ordnance. I have data for several altitudes but I wanted to keep the test flying time down to an hour or less, so I picked the lowest altitude.
Here is the information from the manual:
Table 1: Raw Data from Manual
Altitude, Engine Speed, Supercharger Pressure, Fuel Consumption, Average Speed
0.3 m, 2300 rpm, 1.20 ata, 360 kg/h, 515 km/h
0.3 m, 2100 rpm, 1.10 ata, 225 kg/h, 465 km/h
0.3 m, 2000 rpm, 1.05 ata, 205 kg/h, 440 km/h
There are notes that the fuel consumption is inflated by 12.5% (to allow for a reserve), and the speed is an average of the outbound and inbound legs (presumably to cancel out wind on the test flight).
Correcting for the 12.5% reserve factor, Table 1 becomes:
Table 2: Data From Manual, Adjusted for Reserve Factor
0.3 m, 2300 rpm, 1.20 ata, 320 kg/h, 515 km/h
0.3 m, 2100 rpm, 1.10 ata, 200 kg/h, 465 km/h
0.3 m, 2000 rpm, 1.05 ata, 182 kg/h, 440 km/h
Now how to match this in AH? First we need to convert to appropriate units. Here is the same table expressed in AH units. See the note at the end of this message for consumption rate conversion details.
Table 3: Data from Manual, Converted to AH Units
984 ft, 2300 rpm, 35.9" Hg, 169 percent/h, 320 mph
984 ft, 2100 rpm, 32.9" Hg, 106 percent/h, 289 mph
984 ft, 2000 rpm, 31.4" Hg, 96 percent/h, 273 mph
Now for flight testing. The flight tests were performed offline as follows. Fuel burn rate multiplier was set to 2.5. Fw 190A-8 was selected with 4 x MG 151/20, 2 x MG 131. Fuel load was 25% internal plus a drop tank. Takeoff and climb were accomplished on the drop tank alone. Once altitude was established, RPM and M.P. were adjusted to the desired settings. Speed was allowed to stabilize, then the drop tank was jettisoned and the stopwatch started. Time to burn through the 25% of internal fuel was recorded, and final true airspeed was recorded. Here are the results of the test.
Table 4: Raw AH Flight Test Data
2300 rpm, 36" Hg, Time = 7m15s, Speed = 290 mph.
2100 rpm, 33" Hg, Time = 8m30s, Speed = 265 mph.
2000 rpm, 31" Hg, Time = 9m10s, Speed = 250 mph.
Converting the time to percent/h we get:
Table 5: AH Flight Test Data
980 ft, 2300 rpm, 36" Hg, 207 percent/h, 290 mph
980 ft, 2100 rpm, 33" Hg, 176 percent/h, 265 mph
980 ft, 2000 rpm, 31" Hg, 163 percent/h, 250 mph
To compare "real life" with AH, compare tables 3 and 5. It appears that the AH plane has two major problems. It is too slow at reduced power settings, and the fuel flow rates are too high at reduced power settings.
Where this really hurts is when you look at fuel economy. Divide the the speeds (miles/h) by the fuel flow rates (percent/h) to get the fuel economy in miles/percent.
Table 6: Fuel Economy
2300 rpm, 35.9" Hg, Real Life 1.89 miles/percent, AH 1.40 miles/percent
2100 rpm 32.9" Hg, Real Life 2.73 miles/percent, AH 1.50 miles/percent
2000 rpm 31.4" Hg, Real Life 2.84 miles/percent, AH 1.53 miles/percent
Look at the different trends. A real Fw 190A-8 pilot could get a significant increase in fuel economy by throttling back and reducing RPM. An AH pilot gets a much smaller increase in fuel economy while suffering much larger speed losses.
*Note on Consumption Rate Conversion. The real Fw 190A-8 carried 640 liters of fuel internally. The density of gasoline is about .74 kg/liter which gives a fuel mass of 474 kg. Furthermore my flight test was performed with a fuel burn rate multiplier of 2.5. So to convert a real fuel consumption rate (expressed in kg/h) to percent/h we must divide by 474 kg/tank, multiply by 100 percent/tank, and multiply by the burn rate multiplier of 2.5. The overall result is to multiply by 0.528.
[This message has been edited by funked (edited 09-19-2000).]
