Aircraft AirSpeed

[Traveler]

I don't know why you need 100 MPH and I only needed 84. That's a big difference too. You seem to have missed every relevant point I posted in this thread as well as Rolex's link.

One possible explaination was I did not use flaps.  however the pilots operations manual states that off of land based runways no flaps would be required.  The F6F in the film flys off at 60 knot with the flaps up.  I can fly off the runway at 75 MPH if I use full flaps. 

Would be interesting to know what the source of the performance information was that HiTech Creations used and if that's available online anywhere.

[boomerlu]

I just checked. I got to around 80-90 mph for takeoff at 25% fuel no flaps. Note I am at the edge of stall while pulling up for these.

Auto-takeoff puts the Hellcat around 110 mph.

Nothing seems terribly wrong (i.e., everything you've mentioned seems to be within measurement error).

[FLS]

I should have noted that I didn't use flaps.

Boomerlu because of the acceleration it's easier to see the speed your wheels lose contact if you use film.

The POH gives a 65 Knot power on stall speed in landing configuration for 11000 lbs. 11000 lbs is 25% fuel and no ammo. Wouldn't landing configuration include flaps? The video states you can take off at about 60 Knots. 

[jdbecks]

I should have noted that I didn't use flaps.

Boomerlu because of the acceleration it's easier to see the speed your wheels lose contact if you use film.

The POH gives a 65 Knot power on stall speed in landing configuration for 11000 lbs. 11000 lbs is 25% fuel and no ammo. Wouldn't landing configuration include flaps? The video states you can take off at about 60 Knots. 

maybe in wind? with no wind in AH it might not help with lift?

[FLS]

Wind isn't an issue here. Note that the stall speed is 5 Knots higher than the takeoff speed stated in the film. That probably matched the empty weight stall speed, i.e. no fuel, and might be sloppy editing of the film script, or it just might be the uncorrected IAS, as I noted earlier in this thread.

Taking off in a headwind or tailwind affects your ground speed, not your indicated air speed. IAS is a pressure measurement. That's why it's location affects it's accuracy and the correction for accurate IAS is different in the F6F for flaps up vs flaps down.

In AH the IAS on the gauge is the actual IAS but in the real F6F the IAS on the gauge had to be corrected for different speeds and flap configurations. Then the corrected IAS had to be converted to TAS, true air speed, and you had to allow for wind, in order to navigate over the ocean and find your carrier again.

[jdbecks]

Wind isn't an issue here. Note that the stall speed is 5 Knots higher than the takeoff speed stated in the film. That probably matched the empty weight stall speed, i.e. no fuel, and might be sloppy editing of the film script, or it just might be the uncorrected IAS, as I noted earlier in this thread.

Taking off in a headwind or tailwind affects your ground speed, not your indicated air speed. IAS is a pressure measurement. That's why it's location affects it's accuracy and the correction for accurate IAS is different in the F6F for flaps up vs flaps down.

In AH the IAS on the gauge is the actual IAS but in the real F6F the IAS on the gauge had to be corrected for different speeds and flap configurations. Then the corrected IAS had to be converted to TAS, true air speed, and you had to allow for wind, in order to navigate over the ocean and find your carrier again.

I see, thank you for the clear explanation.

 Did they ever fix the incorrect IAS gauge? or just leave it as it was and continue with the adjustment cards?

[Traveler]

Wind isn't an issue here. Note that the stall speed is 5 Knots higher than the takeoff speed stated in the film. That probably matched the empty weight stall speed, i.e. no fuel, and might be sloppy editing of the film script, or it just might be the uncorrected IAS, as I noted earlier in this thread.

Taking off in a headwind or tailwind affects your ground speed, not your indicated air speed. IAS is a pressure measurement. That's why it's location affects it's accuracy and the correction for accurate IAS is different in the F6F for flaps up vs flaps down.

In AH the IAS on the gauge is the actual IAS but in the real F6F the IAS on the gauge had to be corrected for different speeds and flap configurations. Then the corrected IAS had to be converted to TAS, true air speed, and you had to allow for wind, in order to navigate over the ocean and find your carrier again.

If you review the document at the link given by Rolex it describes the flight test in great detail.  The F6F was tested at the aircraft gross weight of 12410 lbs that full fuel of 250 gals.  The RPM was  set at 2700 for take off but no mention of the manifold pressure used.  Full flaps were used.  They flew it off at 86 MPH.   Not sure I can get any where close to that in AH for the same weight and with the RPM limitation.

[FLS]

2700 is the max RPM. I don't see how that's a limitation.  

At 12400 lbs, full flaps, 2700 RPM, 53" manifold pressure, the AH F6F -5 takes off at 78 mph.    


Jdbecks I'm not aware of any changes to the pitot tube but I'm not an F6F expert. Because of the IAS  inaccuracies there is a controversy regarding the F6F's true top speed. Some people think it was as fast or faster than the F4u but I don't recall which models they were comparing.

[TequilaChaser]

Jdbecks I'm not aware of any changes to the pitot tube but I'm not an F6F expert. Because of the IAS  inaccuracies there is a controversy regarding the F6F's true top speed. Some people think it was as fast or faster than the F4u but I don't recall which models they were comparing.

If memory serves me correctly, they had already moved on to the F7F & F8F , the F6f (all series ) pitot tube was never relocated, except in the tests that took place near the end of the war or post war......

I recall reading they found inconsistencys when doing the F4U vs F6f side by side performance/speed tests...where the F6f-5 was nearly identical as far as speed goes to the F4U ( I forget which version of F4U they was using )

however don't quote me or refer to my above post.. I have not researched/reviewed any of this stuff since 95/97  back when I was doing a write-up on the F6f-3 for AirWarrior Sim

hope this helps..

[wgmount]

The F6F-5's stall speed was 78 Kn (85 mph) how can it take off at a lower airspeed? The maximum spped of the F6F was 330kn it was powered by a 2000hp PW R2800-10. The F4u-1a had a 2250hp PW R2800-8  with a max speed of 380kn.

[FLS]

No aircraft has one stall speed. The stall speed varies according to weight and configuration. If you read this thread carefully you might notice that.

[TequilaChaser]

The F6F-5's stall speed was 78 Kn (85 mph) how can it take off at a lower airspeed? The maximum spped of the F6F was 330kn it was powered by a 2000hp PW R2800-10. The F4u-1a had a 2250hp PW R2800-8  with a max speed of 380kn.

heya Flushed, what are you looking at for your info?

Grumman & Chance Vought did some test near the end of the war or after ( post war ) and found that although the planes were identical or near identical in level flat out speed, their guages were showing (2) different readings, the F6f-5 was showing lower readings than the F4U.....

I will try an go dig up this test/info, so I have something to reference than just my memory....

[wgmount]

I know that FLS but the stall speed I gave was a clean aircraft with 25% fuel. So when you start adding bombs, rockets, ammo, more fuel what happens? so, I'll ask again how do you take an airplane off below the stall speed of one that has no armaments and only 25% fuel.

http://www.history.navy.mil/branches/hist-ac/f6f-5.pdf

Copy of report from a comparison test using an FW-190, F4U-1D, F6F-3
http://home.comcast.net/~markw4/index1.html

[TequilaChaser]

Thanks for the link Flushed(wgmount)

notice on page 2 of that pdf file that it says max speed (mil) for the F6f-5 is 380

and on page 6 of the same pdf file it shows 330 knts at 23,400 ft w/ (1) 150 gallon external tank loaded

[Traveler]

Thanks for the link Flushed(wgmount)

notice on page 2 of that pdf file that it says max speed (mil) for the F6f-5 is 380

and on page 6 of the same pdf file it shows 330 knts at 23,400 ft w/ (1) 150 gallon external tank loaded

take a look at this:  http://www.youtube.com/watch?v=hQ55LmRwkQg