wuzak
Captain
I went away for less than half a day and 4 pages were added.
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Loving this guys! I mention the DMV and we add on 2 more pages! LOL!
RE post # 2926:
The more knowledgeable among us may find this thread infuriating. I think it's perhaps the most informative source I've read about the actual nuts and bolts of flying. My real favorite airplane is the B-17. What drgondog just posted is the part of air war that did'nt make it to the movies.
There have been explanations for:
how planes perform (other than the P-39)
flight planning
aerodynamics
armaments
AND the best running joke ever!
Great thread.
You need to use the fuel consumption at 25000' or 62gph at normal power (2600rpm). You must estimate military power consumption at that height, it is not quoted anywhere in the manual.
Please note that in above examples from the manual that in all but the Minimum cruise (L) the mixture was set to rich. All but the Military rating were at the same altitude.Regarding my estimate for fuel burn at combat power vs normal power, you are correct that going from 2600rpm to 3000rpm is about a 15% increase. That's the increase in fuel burn that I used for my estimate. Throttle setting was the same (full), mixture setting was the same (auto rich), plane was well above critical altitude. Only difference was rpm.
You are entitled to your estimate, but that doesn't make it correct
Chris - when you were taking your flight training did your instructor ever tell you to ignore the climb charts and just calculate your cross country based on range? I know you fly Pipers, love those slide chart!
Charts? What are those? I don't calculate anything. I just hop in and go. I'm an expert.
The other factor that has to be taken into account, is that with large bomber formations, there is turbulence created by the lead bombers, so the ones further back are getting buffeted, causing constant flight attitude correction.RE post # 2926:
The more knowledgeable among us may find this thread infuriating. I think it's perhaps the most informative source I've read about the actual nuts and bolts of flying. My real favorite airplane is the B-17. What drgondog just posted is the part of air war that did'nt make it to the movies.
There have been explanations for:
how planes perform (other than the P-39)
flight planning
aerodynamics
armaments
AND the best running joke ever!
Great thread.
A topic brought up earlier this thread. I just mentally scaled up the fleets of fighters to fleets of bombers. Great thread.The other factor that has to be taken into account, is that with large bomber formations, there is turbulence created by the lead bombers, so the ones further back are getting buffeted, causing constant flight attitude correction.
Hey pben.
He gets it from the P-39Q manual, page 25, chart for 8100 to 7200 pounds ,with 75 gal external tank. First set of columns, there is an entry for 25,000 feet. It says 2600 rpm, 267 mph T.A.S., Full Throttle, 62 U.S. gallons per hour (max continuous power). The climb data from the same manual says it will climb at 750 fpm at 135 mph in a combat climb and 650 fpm at 140 mph in a ferry climb at 25,000 feet. Combat missions were at 3000 rpm and 44..5 " MAP. Ferry mission were at 2300 rpm, 31" MAP (page 23).
When he gets to 25,000 feet, the pilot has to reduce to max continuous (2600 rpm, F.T.), level off, and accelerate to 267 mph. He'd better be quick about it because the range is not much, so he has to turn around rather quickly.
Range is unknown because the range tables are at S.L. and 12,000 feet. Ain't much performance at 25,000 feet. An old Spitfire from 1941 could climb at 3 times the rate, was faster, and had better range.
Let's look at it for the P-39Q. Assume for the sake of argument we are on the drop tank from engine startup, to save arguments and get the best possible result.
87 gallons internal, 75 gallons aux tank. Total = 162 gals.
Climb to 25,000 feet at combat settings takes 13.1 minutes and eats up 39 gallons, leaving 123 gallons, per the manual. Assume we average about 140 mph (goes from 160 mph to 135 mph along the climb for best rate). That moves us forward about 29.5 mile. Let's call it 30 miles.
Assume we cruise at 25,000 feet at max continuous (2600 rpm, F.T., 62 gph burn). We have 36 gallons of aux tank fuel left. That's enough to go for a while 34.8 minutes at 267 mph T.A.S., if we instantly accelerate from the 135 mph climb speed to cruise speed. 34.8 minutes at 267 mph gets us 155 miles farther from home. We are now 155 + 30 = 185 miles from home and we drop the aux tank because it is EMPTY.
Sine we now have no external stores, we use the no external stores chart. Here's where it REALLY gets interesting. We don't change power because we are at full throttle, but our 267 mph T.A.S. with the external tank now magically jumps to 330 mph I.A.S. (if you believe the P-39Q manual). On a standard day, 330 mph I.A.S. becomes 498 mph! So dropping the 75-gallon tank somehow magically makes us accelerate from 267 mph T.A.S. to 498 mph T.A.S. , according to the P-39Q manual.
I think some marijuana was somehow involved in writing this manual. I'll make the assumption that they MEANT to say T.A.S. in both places. So, we now accelerate from 267 mph to 330 mph. Again, pretty doubtful, to me. But, let's run with it.
OK, we now run into our 10 minutes of combat at 25,000 feet and 62 gph and somehow, we manage to engage in this combat at 25,000 feet without losing any height and without getting any close or farther from home. Doubtful, but what the heck, let's ty it. The 10 minutes will eat up 10.33 gallons, leaving us 76.67 gallons of fuel, still at 25,000 feet and 330 mph T.A.S., which takes us 408 miles before we are a glider pilot.
But, suppose I want my half hour of reserve so I'm NOT a glider pilot. That means we only can use 45.6 gallons of the 76.67 gallons we have remaining, still at 25,000 feet and 62 gph, still at full throttle. That means we can only go 243 miles instead of 408 miles.
So, we went 185 miles, had combat for 10 minutes, and we now have 243 miles of range left. Our total distance we can travel will be 185 + 243 = 428 miles, so our combat radius range is now 214 miles and we end up over home base at 25,000 feet with 31 gallons of fuel remaining. Great.
We went from less than 190 miles range from my earlier post all the way to 214 miles range. We gained 24 miles * 2, or 48 miles. Nice.
But, to do that, we needed to be on aux fuel from takeoff (likely against procedures), needed instant acceleration from climb to cruise and instant acceleration from cruise with tank to cruise without tank, needed an instant turnaround at 214 miles, and we needed to have combat joined sometime AFTER we used up the entire aux tank, and also needed the combat to stay at 25,000 feet and get no closer or farther from home.
Offhand, I'd say we needed an absolutely ideal P-39Q mission to get a whole 214 miles from home. Definitely a niche airplane. And my earlier post with 170 - 185 miles of radius would be about right. And I don't think a P-39Q will cruise at 330 mph at 25,000 feet unless there really IS a flying pig somewhere in regular passenger service. At least you don't have to clear the plugs because you're already at full power.
This is futile, but was a bit fun, considering the 498 mph T.A.S. thing. A 498 mph P-39Q? Naahhhhhhhhh ....
Cheers.
Yep - Hempage was rampant during the development of this manual. I think a P-39 might make 498 MPH true while spinning to earth!
I do believe I understand it now. This post wasn't a bunch guys spitting numbers back and forth. Thanks GregP for explaining one side of the argument so I that I could understand the whole picture.Hey pben.
He gets it from the P-39Q manual, page 25, chart for 8100 to 7200 pounds ,with 75 gal external tank. First set of columns, there is an entry for 25,000 feet. It says 2600 rpm, 267 mph T.A.S., Full Throttle, 62 U.S. gallons per hour (max continuous power). The climb data from the same manual says it will climb at 750 fpm at 135 mph in a combat climb and 650 fpm at 140 mph in a ferry climb at 25,000 feet. Combat missions were at 3000 rpm and 44..5 " MAP. Ferry mission were at 2300 rpm, 31" MAP (page 23).
When he gets to 25,000 feet, the pilot has to reduce to max continuous (2600 rpm, F.T.), level off, and accelerate to 267 mph. He'd better be quick about it because the range is not much, so he has to turn around rather quickly.
Range is unknown because the range tables are at S.L. and 12,000 feet. Ain't much performance at 25,000 feet. An old Spitfire from 1941 could climb at 3 times the rate, was faster, and had better range.
Let's look at it for the P-39Q. Assume for the sake of argument we are on the drop tank from engine startup, to save arguments and get the best possible result.
87 gallons internal, 75 gallons aux tank. Total = 162 gals.
Climb to 25,000 feet at combat settings takes 13.1 minutes and eats up 39 gallons, leaving 123 gallons, per the manual. Assume we average about 140 mph (goes from 160 mph to 135 mph along the climb for best rate). That moves us forward about 29.5 mile. Let's call it 30 miles.
Assume we cruise at 25,000 feet at max continuous (2600 rpm, F.T., 62 gph burn). We have 36 gallons of aux tank fuel left. That's enough to go for a while 34.8 minutes at 267 mph T.A.S., if we instantly accelerate from the 135 mph climb speed to cruise speed. 34.8 minutes at 267 mph gets us 155 miles farther from home. We are now 155 + 30 = 185 miles from home and we drop the aux tank because it is EMPTY.
Sine we now have no external stores, we use the no external stores chart. Here's where it REALLY gets interesting. We don't change power because we are at full throttle, but our 267 mph T.A.S. with the external tank now magically jumps to 330 mph I.A.S. (if you believe the P-39Q manual). On a standard day, 330 mph I.A.S. becomes 498 mph! So dropping the 75-gallon tank somehow magically makes us accelerate from 267 mph T.A.S. to 498 mph T.A.S. , according to the P-39Q manual.
I think some marijuana was somehow involved in writing this manual. I'll make the assumption that they MEANT to say T.A.S. in both places. So, we now accelerate from 267 mph to 330 mph. Again, pretty doubtful, to me. But, let's run with it.
OK, we now run into our 10 minutes of combat at 25,000 feet and 62 gph and somehow, we manage to engage in this combat at 25,000 feet without losing any height and without getting any close or farther from home. Doubtful, but what the heck, let's ty it. The 10 minutes will eat up 10.33 gallons, leaving us 76.67 gallons of fuel, still at 25,000 feet and 330 mph T.A.S., which takes us 408 miles before we are a glider pilot.
But, suppose I want my half hour of reserve so I'm NOT a glider pilot. That means we only can use 45.6 gallons of the 76.67 gallons we have remaining, still at 25,000 feet and 62 gph, still at full throttle. That means we can only go 243 miles instead of 408 miles.
So, we went 185 miles, had combat for 10 minutes, and we now have 243 miles of range left. Our total distance we can travel will be 185 + 243 = 428 miles, so our combat radius range is now 214 miles and we end up over home base at 25,000 feet with 31 gallons of fuel remaining. Great.
We went from less than 190 miles range from my earlier post all the way to 214 miles range. We gained 24 miles * 2, or 48 miles. Nice.
But, to do that, we needed to be on aux fuel from takeoff (likely against procedures), needed instant acceleration from climb to cruise and instant acceleration from cruise with tank to cruise without tank, needed an instant turnaround at 214 miles, and we needed to have combat joined sometime AFTER we used up the entire aux tank, and also needed the combat to stay at 25,000 feet and get no closer or farther from home.
Offhand, I'd say we needed an absolutely ideal P-39Q mission to get a whole 214 miles from home. Definitely a niche airplane. And my earlier post with 170 - 185 miles of radius would be about right. And I don't think a P-39Q will cruise at 330 mph at 25,000 feet unless there really IS a flying pig somewhere in regular passenger service. At least you don't have to clear the plugs because you're already at full power.
This is futile, but was a bit fun, considering the 498 mph T.A.S. thing. A 498 mph P-39Q? Naahhhhhhhhh ....
Cheers.
It seems almost all of the discussion is around miss prints and falsified tests. I couldnt understand how getting to 25,000ft was like getting into orbit for one particular aircraft, once there you can cruise at close to maximum speed using just a fraction of the fuel consumption used for climb or flat out runs.Hey pben.
He gets it from the P-39Q manual, page 25, chart for 8100 to 7200 pounds ,with 75 gal external tank. First set of columns, there is an entry for 25,000 feet. It says 2600 rpm, 267 mph T.A.S., Full Throttle, 62 U.S. gallons per hour (max continuous power). The climb data from the same manual says it will climb at 750 fpm at 135 mph in a combat climb and 650 fpm at 140 mph in a ferry climb at 25,000 feet. Combat missions were at 3000 rpm and 44..5 " MAP. Ferry mission were at 2300 rpm, 31" MAP (page 23).
When he gets to 25,000 feet, the pilot has to reduce to max continuous (2600 rpm, F.T.), level off, and accelerate to 267 mph. He'd better be quick about it because the range is not much, so he has to turn around rather quickly.
Range is unknown because the range tables are at S.L. and 12,000 feet. Ain't much performance at 25,000 feet. An old Spitfire from 1941 could climb at 3 times the rate, was faster, and had better range.
Let's look at it for the P-39Q. Assume for the sake of argument we are on the drop tank from engine startup, to save arguments and get the best possible result.
87 gallons internal, 75 gallons aux tank. Total = 162 gals.
Climb to 25,000 feet at combat settings takes 13.1 minutes and eats up 39 gallons, leaving 123 gallons, per the manual. Assume we average about 140 mph (goes from 160 mph to 135 mph along the climb for best rate). That moves us forward about 29.5 mile. Let's call it 30 miles.
Assume we cruise at 25,000 feet at max continuous (2600 rpm, F.T., 62 gph burn). We have 36 gallons of aux tank fuel left. That's enough to go for a while 34.8 minutes at 267 mph T.A.S., if we instantly accelerate from the 135 mph climb speed to cruise speed. 34.8 minutes at 267 mph gets us 155 miles farther from home. We are now 155 + 30 = 185 miles from home and we drop the aux tank because it is EMPTY.
Sine we now have no external stores, we use the no external stores chart. Here's where it REALLY gets interesting. We don't change power because we are at full throttle, but our 267 mph T.A.S. with the external tank now magically jumps to 330 mph I.A.S. (if you believe the P-39Q manual). On a standard day, 330 mph I.A.S. becomes 498 mph! So dropping the 75-gallon tank somehow magically makes us accelerate from 267 mph T.A.S. to 498 mph T.A.S. , according to the P-39Q manual.
I think some marijuana was somehow involved in writing this manual. I'll make the assumption that they MEANT to say T.A.S. in both places. So, we now accelerate from 267 mph to 330 mph. Again, pretty doubtful, to me. But, let's run with it.
OK, we now run into our 10 minutes of combat at 25,000 feet and 62 gph and somehow, we manage to engage in this combat at 25,000 feet without losing any height and without getting any close or farther from home. Doubtful, but what the heck, let's ty it. The 10 minutes will eat up 10.33 gallons, leaving us 76.67 gallons of fuel, still at 25,000 feet and 330 mph T.A.S., which takes us 408 miles before we are a glider pilot.
But, suppose I want my half hour of reserve so I'm NOT a glider pilot. That means we only can use 45.6 gallons of the 76.67 gallons we have remaining, still at 25,000 feet and 62 gph, still at full throttle. That means we can only go 243 miles instead of 408 miles.
So, we went 185 miles, had combat for 10 minutes, and we now have 243 miles of range left. Our total distance we can travel will be 185 + 243 = 428 miles, so our combat radius range is now 214 miles and we end up over home base at 25,000 feet with 31 gallons of fuel remaining. Great.
We went from less than 190 miles range from my earlier post all the way to 214 miles range. We gained 24 miles * 2, or 48 miles. Nice.
But, to do that, we needed to be on aux fuel from takeoff (likely against procedures), needed instant acceleration from climb to cruise and instant acceleration from cruise with tank to cruise without tank, needed an instant turnaround at 214 miles, and we needed to have combat joined sometime AFTER we used up the entire aux tank, and also needed the combat to stay at 25,000 feet and get no closer or farther from home.
Offhand, I'd say we needed an absolutely ideal P-39Q mission to get a whole 214 miles from home. Definitely a niche airplane. And my earlier post with 170 - 185 miles of radius would be about right. And I don't think a P-39Q will cruise at 330 mph at 25,000 feet unless there really IS a flying pig somewhere in regular passenger service. At least you don't have to clear the plugs because you're already at full power.
This is futile, but was a bit fun, considering the 498 mph T.A.S. thing. A 498 mph P-39Q? Naahhhhhhhhh ....
Cheers.
Loving this guys! I mention the DMV and we add on 2 more pages! LOL!
I think there's a few of you in the same boat here! LOL!And I still don't have an answer to my post #2746...and another page has been added since.
Mebbe I'll get an answer one day....but definitely not holding my breath.
I do believe I understand it now. This post wasn't a bunch guys spitting numbers back and forth. Thanks GregP for explaining one side of the argument so I that I could understand the whole picture.
I haven't paid attention to the less dramatic aspects of aviation. I gave up on the jet fighter pilot fantasy when I got my first pair of glasses 60 years ago. That was after my dream of being a Coast Watcher. Studying flight plan prep was at the same level of reading tax codes. No reason to bother with it.
I started following this thread skipping past the numbers. The repartee is gold. That's how I got dragged into The Great Varmint's Burrow of Futility. I couldn't read the official reports posted. What was reprinted was too difficult for my eyes to focus on. So I started paying attention. I started learning (GASP).
Marcel, I am happy these guys keep coming back here.
FTL is right around the corner.
I've asked some honest questions during this protracted "conversation" that have gone unanswered, too.And I still don't have an answer to my post #2746...and another page has been added since.
Mebbe I'll get an answer one day....but definitely not holding my breath.
I've asked some honest questions during this protracted "conversation" that have gone unanswered, too.
It's aparent that the "authority" of Bell Products chooses to avoid engaging in a direct discussion that runs contrary to his beliefs for fear of having to acknowledge the short-comings of his diety.
So in short, yeah, don't hold your breath for a honest/truthful reply from the guy who would be the world's greatest used car salesman...