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

[FLYBOYJ]

I would take a pass on this one. You may not find "combat power" In US manuals.
You might find it in British manuals?
Unfortunately some rather well known authors have used it, rightly or wrongly, Like Francis Dean in AHT.
For instance he used in the acceleration tables I referenced above. This does tend to scramble things.
AS long as every body KNOWS that "combat Power" refers to WEP or WER or some other power level above "military power" I personally don't have a problem with it.
Unfortunately some people don't know the difference.
In the case of the P-39 the difference is mute as the plane can't make anything higher than military power above about 15,500ft.

I actually looked in a British glossary and couldn't find it there either.

 

[Milosh]

I've always heard that about attaining American drivers licenses and renewals. Where I am now and back in my home town of 20K+, I was in and out in less than 20 minutes tops

Can't use the mail or on-line? Only time I go is if a photo has to be taken.

 

[FLYBOYJ]

I just had a thought (dont be alarmed). The P-39 was used a lot as a trainer, are some of these documents applicable to pilot training not operations?

I've seen some separate training manuals written for combat aircraft, never saw one for the P-39

 

[pbehn]

I've seen some separate training manuals written for combat aircraft, never saw one for the P-39

In a training aircraft you may well want the pilot to think for himself for his flight, what he learns doing that is then put into the demands of a mission in service as Bill has described a few times. they are related but different skills

 

[special ed]

Having experienced the normal several hour in person DMV in Louisiana, and particular the New Orleans area, I expected similar in Bay St. Louis, Mississippi. I had bought an old pickup to keep on my in laws' property and went to the local office to register and license it. I arrived at opening time expecting a long wait but found the office empty. Suspecting they had left the door unlocked by accident, I was about to turn when I heard a chorus of young women say, "Over here sir." They had been sitting down behind the counter, so I walked to the nearest one, presented my paperwork, was told to sign a computer generated form, was handed a license plate, a temp title and was told I would receive the actual title in two weeks. I walked to the door in amazement looking at what I had and hesitated a moment when the lady called out, "Is something wrong, sir?" I explained I was used to dealing with Louisiana DMV and was surprised by their efficiency.

 

[drgondog]

Expert - please use the 34 gal per the Op Manual to get to 15K but use no less than 20 gal from your internal tank. Construct a mission scenario from say London to Hamburg ~ 280 miles. Pick R/V near Bremen at 25,000 feet with B-17s moving 150IAS/215 TAS... about 15 minutes short of Hamburg.

You have a group of 48 P-39Q's with whatever load out you choose - but deduct 40mph TAS for 75 gal steel unpressurized tank - and stop using belly tank at 17-18K because you have unpressurized fuel system for those tanks. IIRC P-39 Never had the Mod but P-47C didn't start using the 205 al bathtub Ferry tank until end of July 1943.

Set the boundary conditions as all internal fuel until sometime after take off and formation assembly and initial climb at Take Off and Climb. !2 minutes at MP for Takeoff and MC for orbit to form up at 5K (approx 27 gal internal fuel)

Note from Allison data in Ops Manual that Military Power up to 14,000 is 138gph and Max Continuous is 109gph and Max cruise is 74 up to 14,000. You will climb at Max Continuous Power from Formation assembly over London to Point A (18000 feet) on a straight line. How much external tank fuel will you be able to use before dropping at Point A? Where is Point A.

Tell us when you decide to climb to cruise altitude of 25 K and how far you will go in he climb before you have to switch to internal fuel.

From that point (distance and time to reach 18000 feet) you may use only internal fuel to cruise from 18K to 25 K to RV, cruise to target, essing over the B-17s (if you can, turns are hell with only 750 hp available at 25K).

This will be your key leg. Point A from switch to internal from 75 gal tank at 18K, climb to Point B @25K. Cruise at Max Cruise (2280RPM/31.7 MP - max) to Point C (RV) Ess over B-17s from Point C to Target at D (Maximum Combat Radius). Burn 46 gallons more internal fuel at 20 minutes Military Power over Point D.

Assume 20minutes reserve mandatory for weather, etc.

Questions - How far will you go from base to Point A. Where is that on a straight line to Bremen. How far to climb and cruise on internal fuel to Bremen after you drop tank. (best case for you). What is time for essing to cover Bremen to Hamburg (at 62 gph). How much fuel remains?

Recall that 27K for swith over to 75 gal external. - Remain over base during form up. Climb straight line to Point A on External.

Committed internal fuel with zero cruise fuel available =27 TO/Form, 46 for combat, 20 for reserve -----------> more than 87 gallons. How far can you cruise from A to Hamburg and Hamburg to London? on 120 gallon internal tank.?

 

[FLYBOYJ]

Bill, you rock!

 

[Thumpalumpacus]

Bill, you rock!

Why are you calling him a "rock"? He seems like a smart SoB to me.

 

[33k in the air]

Each state has it's own Department of Motor Vehicles, but oddly enough, the people that staff them all seem to have the same disposition regardless of geographical location.
In all the years of dealing with civil servants, I have rarely had a pleasant (or timely) experience.

So, uncivil servants?

 

[GrauGeist]

So, uncivil servants?

Pretty much...

 

[SaparotRob]

There was a television comedy in which Satan comes to Earth to meet his mortal son (deal gone bad). The son has been compelled to bring escaped souls to the portal of Hell. The portal to Hell is at the DMV.
This is pretty much how we view the DMV here in the U.S.

 

[Thumpalumpacus]

There was a television comedy in which Satan comes to Earth to meet his mortal son (deal gone bad). The son has been compelled to bring escaped souls to the portal of Hell. The portal to Hell is at the DMV.
This is pretty much how we view the DMV here in the U.S.

 

[pbehn]

Bill, you rock!

I dont see what is so difficult to understand but I used to drive between all these places and it is exactly the same for a car if you substitute altitude for passengers. Try booling along at 100mph with three passengers and 4 suitcases with a two litre car, you use almost exactly three times the fuel that you use driving alone at 80-90MPH but with petrol stops and screw ups on the motorway, it takes the same amount of time.

 

[Thumpalumpacus]

I dont see what is so difficult to understand but I used to drive between all these places and it is exactly the same for a car if you substitute altitude for passengers. Try booling along at 100mph with three passengers and 4 suitcases with a two litre car, you use almost exactly three times the fuel that you use driving alone at 80-90MPH but with petrol stops and screw ups on the motorway, it takes the same amount of time.

Or where I live, in the aptly-named Hill Country of Texas, with regular climbs and valleys of up to 600 foot or so, at up to 20% gradients. If you want to maintain speed in the climb, you downshift, increasing revs and manifold pressure, which fuel loss you don't regain on the backside of the hill because you must 1) still be in gear (meaning you're then [finally!] at efficient cruise, for a few moments), and 2) still make adjustments for traffic flow and safe spacing between vehicles, which requires fuel as well as braking.

I have no doubt your experience driving in the mountains, not hills, of Europe, underlines this point even further.

 

[SaparotRob]

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 didn't 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.

 

[pbehn]

Or where I live, in the aptly-named Hill Country of Texas, with regular climbs and valleys of up to 600 foot or so, at up to 20% gradients. If you want to maintain speed in the climb, you downshift, increasing revs and manifold pressure, which fuel loss you don't regain on the backside of the hill because you must still 1) be in gear (meaning you're then [finally!] at efficient cruise, for a few moments), and 2) still make adjustments for traffic flow and safe spacing between vehicles, which requires fuel as well as braking.

I have no doubt your experience driving in the mountains, not hills, of Europe, underlines this point even further.

Well there are no mountains in that area it is almost completely flat, but from the German Border you climb up and before Hanover you descend (on average even on an autobahn it is up and down). On a car with instantaneous and average consumption on the "computer" it was 4 MPG more east to west than west to east. Driving in and around the Alps is a whole new ball game, especially if a tunnel gets shut.

 

[Thumpalumpacus]

Well there are no mountains in that area it is almost completely flat, but from the German Border you climb up and before Hanover you descend (on average even on an autobahn it is up and down). On a car with instantaneous and average consumption on the "computer" it was 4 MPG more east to west than west to east. Driving in and around the Alps is a whole new ball game, especially if a tunnel gets shut.

Wait just a gosh-darn minute! Are you saying driving conditions affect mileage?

Why yes, yes, you are!

How much moreso it must be for a vehicle that doesn't have the ground in place supporting it ...

I've driven through some good mountain ranges, and my experience is that the more elevation and directional changes I drive through, the more fuel my crate uses. Engines like simplicity, which is a word no combat-pilot would use to describe forming up and setting out on a 500-mile round-trip.

 

[wuzak]

Committed internal fuel with zero cruise fuel available =27 TO/Form, 46 for combat, 20 for reserve -----------> more than 87 gallons. How far can you cruise from A to Hamburg and Hamburg to London? on 120 gallon internal tank.?

Assuming, of course, that your P-39 is fitted with the 120 gallons worth of fuel tanks.

 

[FLYBOYJ]

Loving this guys! I mention the DMV and we add on 2 more pages! LOL!

 

[wuzak]

Test weights were average weight for that flight, starting with full fuel and landing with a small reserve. British used 95% of published gross weight as the noted weight in their tests. None of the official Wright Field tests were noted at the published gross weight of the plane. None in wwiiaircraftperformance.org anyway.

I believe the British corrected performance to 95% of gross weight. Not tested at 95% gross weight, since the weight varied during a test flight.