Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (5 Viewers)

FLYBOYJ said:
So let me put this out there to my fellow pilots, especially Wes, Bill and Biff (if you wish to partake in this groundhoggery) who are all ATPs and have way more time in the air than this Commercially Rated CFII who only flies SEL aircraft - how would you interpret this?
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I haven't got time to dig into the charts right now, but rule of thumb if you don't want your pilots to take an unscheduled swim: ALWAYS take the LEAST optimistic figure, then start deducting for contrary circumstances from there. Tail End Charlie will be flying the most beat up least efficient plane in the squadron, will burn the most fuel throttle jockeying at the whiplash end of the formation, and be the one whose loss you'll have to explain to the CO and whose parents you'll have to write THE LETTER to after everybody else returns safe.
 
FLYBOYJ said:
I posted the charts for the P-39 N and Q and both sets of flight operation instruction chart contain this statement, varying with configuration:

View attachment 632942

So that chart tells me that there is a 20 gallon allowance for warm up and climb to 5000'.

BUT on the climb data chart we have this:

View attachment 632943

it also says this on the bottom of the same chart;

View attachment 632944

If you look at the climb chart and flight operation instruction chart. they are in conflict with each other as the climb to 5000' is more than 20 gallons (depending on weight)

View attachment 632945


So let me put this out there to my fellow pilots, especially Wes, Bill and Biff (if you wish to partake in this groundhoggery) who are all ATPs and have way more time in the air than this Commercially Rated CFII who only flies SEL aircraft - how would you interpret this?

View attachment 632946
Click to expand...
If there is a 20gal allowance for takeoff and climb to 5000', then why are other altitudes listed on the chart? And why aren't there specific allowances for every altitude? Because the 20gal allowance works for all the altitudes and power settings for the chart. Fuel used during climb and the cruising range during that climb are already factored in. To make it easier for the pilot to use the chart.
 
P-39 Expert said:
Because the 20gal allowance works for all the altitudes and power settings for the chart. Fuel used during climb and the cruising range during that climb are already factored in. To make it easier for the pilot to use the chart.
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No way, Jose! There are no "one size fits all"s in aircraft performance. Any competent pilot, when presented with one, had better adopt a "show me" attitude and verify its accuracy if surviving to old age is important to them. Your armchair won't dump you in the drink; your P39 will.
 
Marcel said:
My conclusion is that there must be some masochistic tendencies amongst the members of this forum. It's the only way I can explain that this discussion is still raging.
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It's a manifestation of our sense of brotherhood and charity that we will put in all this effort to help our wayward member see the light, despite his mental attributes apparently resembling those of a creature whose contribution to the breakfast table we worship here, and whose feral cousin totes a 30MM firehose and hunts diesel armadillos for a living. Don't you find that honorable?
 
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P-39 Expert said:
If there is a 20gal allowance for takeoff and climb to 5000', then why are other altitudes listed on the chart? And why aren't there specific allowances for every altitude?
Click to expand...

There are. It's right there on the Take-Off, Climb, and Landing charts page. An image of it has been provided in this post.

At 8,000 lbs take-off weight:

24.5 gallons used to 5,000 feet
29.2 gallons used to 10,000 feet
35.3 gallons used to 15,000 feet
39.7 gallons used to 25,000 feet

The higher you go the more fuel is going to be used because more energy must be expended to get higher up. Basic physics.
 
P-39 Expert said:
If there is a 20gal allowance for takeoff and climb to 5000', then why are other altitudes listed on the chart? And why aren't there specific allowances for every altitude? Because the 20gal allowance works for all the altitudes and power settings for the chart. Fuel used during climb and the cruising range during that climb are already factored in. To make it easier for the pilot to use the chart.
Click to expand...
There's also a relief tube to make it easier on the pilot.

Wes said it - it isn't "one size fits all." You are so wrong in so many fronts and now you're going to try to dispute this was an ATP. Incredible! This is why I stopped addressing this many posts back. You don't know how to use the charts, that simple, the same way you didn't know how to do weight and balance so you can continue with your narcissist belief that you know what you're doing, there are some of us who have actually used similar charts for actual flights. So tell us, how many cross country flight hours have you flown calculating flight data?

BTW - I will say that there are errors on those charts and missing data so I will give you that. Aside from that all is good if you plan to take off and fly at 5000' all day!
 
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XBe02Drvr said:
No way, Jose! There are no "one size fits all"s in aircraft performance. Any competent pilot, when presented with one, had better adopt a "show me" attitude and verify its accuracy if surviving to old age is important to them. Your armchair won't dump you in the drink; your P39 will.
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From the little I have read compared to others who post, the mission planners had the power to inflict more losses on their own than the opposition. Imagine the bombers not being escorted because of a screw up in timing, not being able to land because of weather and the escorts ditching, running out of fuel trying to find them.
 
Glider said:
You have never answered this question which has been put a number of times.

If the P39N (the one you always quote) was so good, why did they produce thousands of the P39Q?
b) Every other combat aircraft I can think of improved with the exception of the P39, why was that?
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As a military plane the P-39 improved the way that a Typhoon improved, according to what the client wanted, it was reinforced and had armour added to make it more useful, not faster or better climbing. The Q had a lot of mods that the Russians asked for, who seemed to have similar ideas to the British.
 
FLYBOYJ said:
Hmmm - "combat power vs normal power"

Word search no such thing...

"Military Power/ Takeoff Power" found in manual.
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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.
 
Shortround6 said:
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.
Click to expand...

AAARRGGGHHHH....one of my pet peeves of the English language: mute = silent, speechless; moot = debatable, doubtful. Methinks you mean the latter.

I'm clearly too grumpy to continue posting to this thread. I'm off to bed.

P.S. Apols SR6...just couldn't resist! :)
 
fubar57 said:
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
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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.
 
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