Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: F4UDOA on August 02, 2000, 09:13:00 PM
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Pyro,
I'am really beating a dead horse I know but as long as 1.04 hasn't come out yet I thought I would throw one more log on the fire.
The power on full flap stall speed right out of the F4U-1D manual is
11,300LBS Full Flap(50Degrees)=76MPH IAS
11,300LBS 20degrees flap no power=91MPH IAS
11,300LBS Full Flap no power=86MPH IAS
The F4U-1D in a fighter configuration full fuel weighed 11,962LBS. It carried a full tank of intenal fuel weighing 1422lbs. At 50% fuel it Weighed 11,251LBS. So it should stall full flap power on at slightly under 76MPH IAS with 50% fuel. Currently it stalls at approx. 100MPH with the same load. Just one more gratuitous F4U factoid from yours truely.
Thanks Again
Master of the Obvious
F4UDOA
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I'll have to take a look at the manual but I can look at the numbers you cited and tell that they're off. You need to make two conversions to that number before you can directly compare it to AH figures. First, USN used knots instead miles so you need to convert to miles. 1.15 multiplier. Second, IAS figures will differ from our IAS because we don't model airspeed error due to pitot placement, etc., so in AH IAS=CAS. There is usually a conversion chart for that in one of the manual's appendixes for converting IAS to CAS.
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Doug "Pyro" Balmos
HiTech Creations
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My apologies if you already did that. I was spacing when I originally looked at it and thought you were citing a clean configuration.
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Doug "Pyro" Balmos
HiTech Creations
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Question. I know what IAS is. I know what TAS is. WTF is CAS?
Swoop
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Originally posted by Swoop:
Question. I know what IAS is. I know what TAS is. WTF is CAS?
Swoop
Calibrated Air Speed. If I am right (quite possible I am not) the IAS always has a +-% of instrumental error, the CAS accounts for this error.
You might call it True indicated airspeed (http://bbs.hitechcreations.com/smf/Smileys/default/biggrin.gif)
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cheers RAM. :-)
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Swoop
Well into the 'who cares' category, are the terms IAS, CAS, and EAS. Briefly...
IAS - Indicated Airspeed. What we see on the airspeed indicator. May have minor errors due to mechanical errors in the actual instrument.
CAS - Calibrated Airspeed. IAS corrected for 'position errors'. Position errors occur when the aircraft flys through its speed envelope in varying configurations (gear, flaps, external stores, etc). These errors are usually very small, so many folks just round them off and refer to CAS and IAS as being the same. All of this depends on the specific aircraft type. More often than not, the position error value is subtracted from the IAS to get CAS.
EAS - Equivalent Airspeed. CAS corrected for compressibility. Compressibility becomes a factor as the aircraft speed increases. In a high speed jet, these correction values can be as much as 5-10%. Usually, the compressibility factor (CF) is subtracted from CAS, ie if CAS=300, CF=25, therefore EAS=275.
Then there is TAS (True Airspeed). TAS is the actual speed of the aircraft through the air without reference to the ground. TAS takes into account the altitude and ambient temperature of the air. Generally speaking, as the aircraft climbs, the TAS value becomes larger than IAS value.
Because of this, this one can be tricky for us since many references to max performance give the speed in TAS, not IAS. So when you see a max speed at a certain altitude as being 400 mph, that means 400mph in TAS...the IAS that the pilot is seeing on the cockpit airspeed indicator is usually somewhat less. Also, these max speed values usually mean the max speed that the aircraft can accelerate to in 1 G level flight. As such, the listed speed is really good only as a comparative reference, since it is not the speed that you see on the airspeed indicator, nor is it the overall max speed that the aircraft could reach in a dive.
Hope this helps!
Andy
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"Well into the 'who cares' category.."
Well. I don't understand 90 % of what you, Pyro, F4UDOA, Wells or Badboy say in these disussion but I find it very interesting and I try to learn somehting from all of it.
So who cares? I do for one. Don't worry about those who don't.
-Westy
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Looked over your post again this morning. On the power on stalls - HT has already caught an error on my part regarding propwash figures when he was looking through things that could be off. I've got to jump back in and do some fixing in that area. As for the power off figures, I'll take a look at it.
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Doug "Pyro" Balmos
HiTech Creations
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Thanx Pyro,
I know I seem like I am wining, but you guy's are the first flight simm on the market that cares about really getting it right. I didn't notice this until I broke out my F4U pilots manual. I just never noticed the stall speed table before.
Anyway there is a correction table for CAS in the manual if you have it. Anyway here it is. "The calibration below represents the air speed head position(pitot tube) and gives the corrected indicated air speed for a given reading of the cockpit airspeed indicator assuming zero scale error for the intsrament itself."
IAS=90knts CAS=88knts error -2knts
IAS=100knts CAS=99Knts error -1knt
IAS=110KNTS CAS=110KNTS error 0
Correction with flaps
IAS=70knts CAS=67knts error -3knts
IAS=80KNTS CAS=78KNTS error -2knts
IAS=100KNTS CAS=100KNTS error 0
High speed error
IAS=260KNTS CAS=266KNTS error +6KNTS
IAS=280KNTS CAS=287KNTS error +7knts
IAS=300KNTS CAS=308KNTS error +8KNTS
By the way I already did the conversion to MPH from KNOTS. The stall speed stated for full flap power is 66KNTS IAS. I converted that to 76MPH using this site that has a conversion tool for metric and Nautical miles
http://www.french-property.com/ref/convert.htm#mass (http://www.french-property.com/ref/convert.htm#mass)
I did this for all speeds.
Hope this helps.
Later
F4UDOA
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Does anyone have a copy of the F4U flight manual on line or in an electronic copy to email?
Pyro,
Did you check my last post? It was already converted from Knots to MPH.
Thanx
F4UDOA
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what a cool thread ,thanks pyro
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Yeah, I caught all that when I checked the manual. I originally thought it must have been off in that area because I read it wrong and thought you were talking about a clean condition.
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Doug "Pyro" Balmos
HiTech Creations
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Just a little question...
How were the wind conditions?
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Fishu,
Those numbers come out of the F4U-1D pilots manual. No wind conditions stated. I suppose since there measued in IAS then air flow over the pitot tubes is already factored in. However I may be wrong. I'm just giving a best guess for that one. All speeds and performance in AH is based on a perfect airplane and a perfect day except for wind at some alt, so I guess these numbers are pretty much baseline.
Thanks
F4UDOA
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Just on the topic of 'who cares' because no one asked, I thought i'd throw this in, just in case anyone was wondering (sorry i'm a sailor)
1 nautical mile = 2000 yards
1 knot = 1 nautical mile per hour
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Hamish!
(http://pages.hotbot.com/games/davekirk/images/Logos.jpg)
[This message has been edited by Hamish (edited 08-07-2000).]