Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained)

[P-39 Expert]

First of all, 200 yards is 600 feet or roughly an eighth of a mile - this is a distance where many fighters engaged.
They didn't stand off and shoot laser beams at five miles.
As for the piddly .30 caliber, the Axis types claimed thousands of Allied air craft with their piddly 7mm MGs.
The British held the Luftwaffe at bay with their piddly .303s during the Battle of Britain.
So why was that?
Did it possess a mystical P-39ish power that defies physics?
Or was it simply because a .30/7mm round will pass through wood, aluminum skin, glass and human bodies at ranges over 3,000 feet.

And entire world war was being fought with .30/7mm weapons before the US entered. They just didn't sit around for four years (in the Orient) and two years (in Europe) wondering what they could use to shoot down an enemy aircraft - the .50 delivered a harder punch, doing more damage for each round delivered, yes, but just because an aircraft was armed with them, didn't mean it had invincibility.
A KI-43 could shoot down a P-40 armed with .50MGs just as easy as it xould shoot down a P-40 armed with .30MGs.

Regarding the .30 armed P-40, there were several hundred manufactured (not including exports) before the D model.
They saw action at Pearl Harbor, the Philippines and other areas of the Pacific.

The SBD was one of the first US aircraft to be designed and built with the .50MG as it's armament (two in the cowl). Up to that point, it was common for fighters to have a mix of one .30 and one .50 OR being being solely armed by .30s, which, prior to WWII, was a world standard.

Most AAF/USN fighters had their wing 50cals harmonized at 300-350 yards.

 

[P-39 Expert]

OK, back from a week in Las Vegas. Boy, was it hot!

From a couple of days back, I posted something that got some good reactions because I used a Monty Python Shakspearian type insult for the P-39. Now, as promised, you, too, can insult people and airplanes with aplomb.

I offer this spreadsheet. either pick one choice from each of three columns or follow the instruction to generate a random insult. This is not password protected, but insult away at your own risk. I assume no liability for your musings using this handy insult reference.

Enjoy, you loggerheaded clay-brained malt-worm! That insult was from inputting 24, 7, 33 into the inputs after you enable editing.

I have another spreadsheet for coming up with proposal buzzwords.

For instance, if I input a 3-digit number, say ... 257 ... into the buzzword spreadsheet, I get "systematized logistical projection." It is a phrase that can be dropped into virtually any report with that ring of decisive knowledgeable authority. No one will have the remotest idea of what you are talking about, but the important thing is THEY ARE NOT ABOUT TO ADMIT IT.

I attached it, too. Enjoy, and don't get fired using this crap. It's all for fun only.

Your weight and balance spreadsheet was much more useful.

 

[pbehn]

Ducted air heating system was present on the P-39D.

Regarding your last paragraph, the ducted air heat system on the domestic models was much superior to the gas fueled system on the export models so it was discontinued. For impact on frozen pilots, see the P-38.

I thought the heating system was for the guns as well as the pilot?

 

[P-39 Expert]

I stopped debating flight manual charts with you because you don't now how to use them properly and refuse to listen to people on here who are actual pilots and flown real airplanes, and I don't want to continually bang my head against the wall. There is no "combat reserve" or "landing reserve," that is calculated within your flight planning. A 30 or 45 minute reserve is what is normally planned into a mission should something happen and you have to extend. It's quite obvious that many missions were flown well into the reserve calculation.

I'm not going to debate this with you!!!!

To the other members partaking in these discussions, any "calculations" our friend here comes up with regards to flight planning and using flight manual charts, I would really double check if you have access to the data/ flight manual.

I'm simply using the Flight Operation Instruction Chart according to the directions provided. "If the original flight plan calls for a mission with changes in power or speed the flight should be broken down into a series of individual short flights and then added together to make up the total flight and it's requirements." 20 minutes of combat would be at a higher power setting and 20 minute reserve for landing would be at a lower power setting.

I really don't understand what there is to debate.

 

[GrauGeist]

Most AAF/USN fighters had their wing 50cals harmonized at 300-350 yards.

The convergence points varied greatly, depending on type, mission, weapon arrangement, theater and time period.

Some pilots even had their own formulas, like Lt. Drew's P-51D, which was up for three points of convergence:
200 yards, 250 yards and 300 yards.

Maj. Chick had his P-47D set up for 100 yards.

And on the other side of the fence, Erich Hartmann had his Bf109 set up for 53 yards.

The further the distance to target, the higher the need for deflection aiming. The closer to target, the higher the probability of saturating the target.

 

[buffnut453]

Ducted air heating system was present on the P-39D…the ducted air heat system on the domestic models was much superior to the gas fueled system on the export models so it was discontinued.

But the P-39C was a domestic model and it had the gas heater. S Shortround6 also provided pilot manuals for the D-1 and D-2 which also showed they had the gas heater.

Please provide a source for your assertion that the D had ducted air heating.

 

[P-39 Expert]

Okay, here's what I'm trying to figure out. Remember the map of Europe posted once, having concentric circles indicating fighter escort ranges? Had it been there, how far would the semi circle go for the the P-39? Say mid 1943.

Using a P-39N with 120gal internal and 110gal drop tank (230gal) deduct 20gal for takeoff and climb, 25gal for 20min combat at 25000' and 10gal for 20min landing reserve at 5000'. The remaining 175gal (cruise) is divided by 62gallons per hour giving a flight time of 2.8hrs multiplied by 276mphTAS = 772mi. Half that is the combat radius 385mi. Be conservative and say 370mi. For perspective Berlin was 520mi.

This is carrying the drop tank the whole mission. If the tank is dropped then cruising speed increases to 350mph at the same power (62gph) and range increases accordingly.

 

[Vincenzo]

Using a P-39N with 120gal internal and 110gal drop tank (230gal) deduct 20gal for takeoff and climb, 25gal for 20min combat at 25000' and 10gal for 20min landing reserve at 5000'. The remaining 175gal (cruise) is divided by 62gallons per hour giving a flight time of 2.8hrs multiplied by 276mphTAS = 772mi. Half that is the combat radius 385mi. Be conservative and say 370mi. For perspective Berlin was 520mi.

This is carrying the drop tank the whole mission. If the tank is dropped then cruising speed increases to 350mph at the same power (62gph) and range increases accordingly.

your calculation is fault, you can not choice when drop the tank, at best it's just before of fight, so 120-55=65 so your radius is around 1 hour, if you are not attacked before

 

[FLYBOYJ]

I'm simply using the Flight Operation Instruction Chart according to the directions provided. "If the original flight plan calls for a mission with changes in power or speed the flight should be broken down into a series of individual short flights and then added together to make up the total flight and it's requirements." 20 minutes of combat would be at a higher power setting and 20 minute reserve for landing would be at a lower power setting.

I really don't understand what there is to debate.

There is NO "RESERVE" for landing - that part of the flight is factored into the entire flight plan unless you intend to fly at military power over the field for 20 minutes (or whatever your emergency reserve is, usually 30 to 45 minutes). Pilot 101, or in your case "Joe Pilot".

"reserve" "tail cone" "in balance" "Joe pilot" Groundhog jargon.

You're right, there is nothing to debate

 

[P-39 Expert]

I thought the heating system was for the guns as well as the pilot?

It was, heated cockpit air was ducted from the rudder pedal wells up to blow directly on the cannon and twin 50calMGs and then exhausted through the small exit ducts near the nose. Very efficient system.

 

[pbehn]

Using a P-39N with 120gal internal and 110gal drop tank (230gal) deduct 20gal for takeoff and climb, 25gal for 20min combat at 25000' and 10gal for 20min landing reserve at 5000'. The remaining 175gal (cruise) is divided by 62gallons per hour giving a flight time of 2.8hrs multiplied by 276mphTAS = 772mi. Half that is the combat radius 385mi. Be conservative and say 370mi. For perspective Berlin was 520mi.

This is carrying the drop tank the whole mission. If the tank is dropped then cruising speed increases to 350mph at the same power (62gph) and range increases accordingly.

I hope you forward this to your opponent as your terms of engagement. What are your cruising figures at 25,000ft and how long does it take to get there? P-39 Performance Tests

 

[P-39 Expert]

There is NO "RESERVE" for landing - that part of the flight is factored into the entire flight plan unless you intend to fly at military power over the field for 20 minutes (or whatever your emergency reserve is, usually 30 to 45 minutes). Pilot 101, or in your case "Joe Pilot".

"reserve" "tail cone" "in balance" "Joe pilot" Groundhog jargon.

You're right, there is nothing to debate

There is a reserve for landing in case the base is closed by weather or the pilot becomes lost. And 10 gallons of fuel certainly won't let the pilot cruise at low altitude at military power for 20 minutes. How is landing the plane factored into the entire flight plan without creating a reserve for that section of the flight?

I thought we weren't going to debate this anymore.

 

[P-39 Expert]

your calculation is fault, you can not choice when drop the tank, at best it's just before of fight, so 120-55=65 so your radius is around 1 hour, if you are not attacked before

Certainly ANY fighter with external tanks must return early if forced to drop the tanks before their fuel is exhausted.

 

[FLYBOYJ]

There is a reserve for landing in case the base is closed by weather or the pilot becomes lost. And 10 gallons of fuel certainly won't let the pilot cruise at low altitude at military power for 20 minutes. How is landing the plane factored into the entire flight plan without creating a reserve for that section of the flight?

I thought we weren't going to debate this anymore.

I wasn't debating I was pointing out that your armchair flight training is once again wrong.

Yes there is no debate. You can believe what you want - if pilots (joe Pilots and test pilots included) did their flight plans the way you have described in some of your post, parachute companies would have made a lot more money. I want the rest of the membership to see your errors and it seems they already have.

No debate - just facts...

 

[pbehn]

If a 110 gallon external tank has so little effect on performance why would they ever get dropped? What was the cruise speed power setting at 25,000ft with a 110gal tank?

 

[Vincenzo]

Certainly ANY fighter with external tanks must return early if forced to drop the tanks before their fuel is exhausted.

but in your example the tank is too large for the internal fuel available, the tank is usable only for the cruise in, a tanker larger of 70 gal for the P-39 with 120 gals, if your info on the consume are right, is useless, is a waste of fuel

 

[GregP]

Regarding Post 2747, if you drop the tank, yes, the speed increases, but you also lose all the fuel remining in the drop tank.

Figure it will be dropped on the way into the target since the enemy KNOWS you need the drop tank or you wouldn't have one in the first place. If I were the enemy, I'd send in fighter to hit as soon as possible so their ranges would be greatly reduced.

 

[Shortround6]

Basic combat radius.

120 gallons internal.
Minus 10-15 gal for take-off. Some fuel will be slowly returned in cruise.
Minus your 10-14 gallon "landing reserve".
Minus your combat allowance.
That is the fuel you have to get home after dropping the tank/s.

If you are only burning 25 gallons in 20 minutes you aren't making enough power to win in combat.

 

[pbehn]

This is carrying the drop tank the whole mission. If the tank is dropped then cruising speed increases to 350mph at the same power (62gph) and range increases accordingly.

I dont think there can be any doubt now that you are just trolling. The maximum speed of the P-39N was about 375MPH, its cruising speed at 15,000ft cruising altitude was 250MPH, Your consumption in cruise at 62gph is only marginally less than your combat 25 gals in 20 mins that is 75gph. most engines used circa 3 times the fuel on max power that they used in cruise.

BTW the idea of escorting bombers flying at 25K while you are at 15K is just funny, not only does it take 6 minutes to get up there, you would have many missions flying in cloud and hopelessly lost.

 

[33k in the air]

Using a P-39N with 120gal internal and 110gal drop tank (230gal) deduct 20gal for takeoff and climb, 25gal for 20min combat at 25000' and 10gal for 20min landing reserve at 5000'. The remaining 175gal (cruise) is divided by 62gallons per hour giving a flight time of 2.8hrs multiplied by 276mphTAS = 772mi. Half that is the combat radius 385mi. Be conservative and say 370mi. For perspective Berlin was 520mi.

This is carrying the drop tank the whole mission. If the tank is dropped then cruising speed increases to 350mph at the same power (62gph) and range increases accordingly.

Your calculations are incorrect.

(1) The P-39N-0/1 consumed 147 gallons per hour at full military power. The usual rule for combat fuel allowance was 15 minutes at full military power and 5 minutes at war emergency power. The latter isn't listed on the charts, so let's just go with 15 minutes of full military power.

147 / 60 * 15 = 36.75 gallons

The combat fuel allowance is closer to 37 gallons, not the 25 gallons you stated.

(2) At a take-off weight of 8,000 lbs, the P-39N-0/1 consumed a total of 39.7 gallons of fuel to climb to 25,000 according to the climb data section of the Take-off, Climb, and Landing chart.

The fuel consumed in climbing to 25,000 feet is closer to 40 gallons, not the 20 gallons you stated.

(3) Reserve fuel allowance normally used in radius calculations is thirty minutes, not twenty. Using Column V (max. range) for 7,500 to 7,100 lbs weight, fuel consumption per hour is about 35 gallons per hour. Call it 17 gallons for half an hour.

The fuel reserve is 17 gallons, not the 10 gallons you stated.

(4) The combat radius is determined by how far the aircraft can fly back on internal fuel after deducting allowances for warm-up, initial take-off, combat, and reserve (assuming the cruise out can be done mostly on external fuel in drop tanks).

At 120 gallons full internal: 120 - 37 - 17 = 66 gallons left to cruise back to base.

(Note that the internal fuel remaining would actually be slightly less than 66 gallons, since warm-up, take-off, and initial climb are done on internal fuel before switching over to external fuel. But let's use 66 to be generous.)

Using your own figures of 62 gallons per hour at a TAS of 276 MPH for the cruise back yields the following:
66 / 62 * 276 = 293.8 miles


See the relevant charts on pages 26-28 of the PDF found here:
Pilot's Flight Operating Instructions -- P-39N-0 and P-39N-1 Airplanes