Landing speed and corresponding AOA?

The F-35 compared with other modern jets.
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gta4

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Unread post23 May 2017, 14:48

Some people claims F-35 requires a high AOA to maintain level flight thus reducing its aerodynamic efficiency. However the evidence below contradicts this:

The following is a combination of landing speed and AOA from different sources:

F-35: 13 deg AOA at 150 knots, with 5000lbs fuel burnt:
https://www.aopa.org/news-and-media/all ... ight-stuff

Rafal: 16 deg AOA at 125 knots, with 15 ton total weight:
https://www.flightglobal.com/news/artic ... le-334383/

M346: 12 deg AOA at 150 knots, and 14 deg AOA at 128 knots, with 900kg fuel burnt:
https://www.flightglobal.com/news/artic ... or-207881/

The F-35 has almost the same required AOA as other aircraft. Anyone can get this data from F-16 flight manual?
Last edited by gta4 on 23 May 2017, 15:50, edited 2 times in total.
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vilters

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Unread post23 May 2017, 15:11

Your numbers are nit complete without the weights;

For the F-16A it was: 125 kts at 13°AOA => "PLUS 5 kts" for each 1000lbs above empty weight.
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gta4

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Unread post23 May 2017, 15:49

"PLUS 5 kts" for each 1000lbs above empty weight.


Linear model?

Should be a power of 0.5 or something similar.
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35_aoa

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Unread post24 May 2017, 00:44

gta4 wrote:
"PLUS 5 kts" for each 1000lbs above empty weight.


Linear model?

Should be a power of 0.5 or something similar.


That was just the "gouge" for the A/B. I'm sure an engineer could nerd out and find exceptions to the rule, but at the end of the day, it was just a rough crosscheck to make sure your AoA vanes weren't lying to you.......since you aren't really paying attention to indicated airspeed during the approach, but rather AoA.

Similar "gouge" numbers were used for overhead SFO approaches. There was a base fuel weight (off the top of my head, think it was 2k in the B, and 3k in the A), and you adjusted the high key number corresponding to those base weights +500 ft for every 1000 lbs of gas above that, and low key +250 feet. Not at all an exact science, but a simple rule of thumb you could run in your head and get in the ballpark of the energy state you needed to make the runway if the pattern is flown correctly. Or you can just do the more likely straight in SFO, and pitch over when the flare point is 11-17 degrees depressed from the horizon without doing any math.....much mo easier.
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gta4

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Unread post24 May 2017, 01:19

35_aoa wrote:
gta4 wrote:
"PLUS 5 kts" for each 1000lbs above empty weight.


Linear model?

Should be a power of 0.5 or something similar.


That was just the "gouge" for the A/B. I'm sure an engineer could nerd out and find exceptions to the rule, but at the end of the day, it was just a rough crosscheck to make sure your AoA vanes weren't lying to you.......since you aren't really paying attention to indicated airspeed during the approach, but rather AoA.

Similar "gouge" numbers were used for overhead SFO approaches. There was a base fuel weight (off the top of my head, think it was 2k in the B, and 3k in the A), and you adjusted the high key number corresponding to those base weights +500 ft for every 1000 lbs of gas above that, and low key +250 feet. Not at all an exact science, but a simple rule of thumb you could run in your head and get in the ballpark of the energy state you needed to make the runway if the pattern is flown correctly. Or you can just do the more likely straight in SFO, and pitch over when the flare point is 11-17 degrees depressed from the horizon without doing any math.....much mo easier.


Thanks.

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