Takeoff speed

[Teej]

Hey Haole (or any of the crew who know)...

What's the range of takeoff speeds based on weight?

Having a little...discussion...over on Frugal's. One opinion is that the jet will, at any load within limits, take flight between 150-160 knots with 10 degrees nose up. The other opinion is that a sufficiently loaded plane (say, 3 external tanks plus slammers & Mk84s)...41,000 plus...close to MTOW...will not lift off the ground until significantly faster (say, 180+)

Any hard data for us?

Thanks bud.

:beer:

[Buckshot]

180 sounds way too high to me, I'm sure Haole or one of the other pilots will be able to give a better indication. If I get a chance I'll check the pilot manual and see what it says.

[Teej]

Well, I know Falcon is often short on reality no matter how hard the guys try with the flight models...but for what it's worth this was loaded down with 3 external tanks (2*370 + 300), 4 slammers & f4 GBU 35s. Was making the plane as heavy as I could. In a block 50 it broke 42000 slightly...in a 52, it ran 417xx.

I hit the gear switch going down the runway at MIL power so I'd be able to tell the instant weight came off the wheels.

I rotated at 155 and held 10-11 nose up until 169 with no lift. At that point, running out of tarmac, I lit the pipe and the wheels went in transit at 185.

This is, of course, a game, not reality....as evidenced by the fact that I can grease a landing when loaded like that. :)

[SUBS17]

Does the aircraft allow you to do that in RL, can you hit the gear switch while on the runway and will it automatically raise after the weight is off. Just curious thats the first time I've ever heard of that one.

[Teej]

Does the aircraft allow you to do that in RL, can you hit the gear switch while on the runway and will it automatically raise after the weight is off. Just curious thats the first time I've ever heard of that one.

I doubt any real pilot is dumb enough to try. :)

It's pretty dangerous even in the game. You can get a little lift on the rotation...enough that the landing gear struts bounce you off the ground enough to satisfy the WOW sensor that you're not on the ground...but you don't really have the speed to sustain flight and you'll settle back down and crash.

[Sappy]

Weight certainly will affect takeoff speed. For an F-16C loaded to near maximum allowable GW, CG 35% and 12 degree pitch, the takeoff speed will be around 180+ KIAS. Lower that pitch to 10 degrees and you can add a few more knots.

[DEX]

Does the aircraft allow you to do that in RL, can you hit the gear switch while on the runway and will it automatically raise after the weight is off. Just curious thats the first time I've ever heard of that one. I can't speak for a Viper but if you look at the WOW logic of most aircraft, it should technically be possible. Now if things aren't calibrated just right, get ready for some paperwork. For instance, in the aircraft at one particular FBO I used, the WOW micro-switch -- there is a technical term but that's the essence of it -- was supposed to prevent accidental gear retraction on the ground. However, maintenance preferred to fill the struts such that the WOW switch was never depressed. This was because there was a high volume of training activity at that location and the increased strut height reduced the likelihood of the aircraft bottoming out on a rough landing. In this case, gear up meant gear up, on the ground or not. No incidents, though.

Teej is right, noone's gonna try that one and yes, just because the aircraft gets light enough on the wheels for WOW to think you're airborne doesn't mean you're good to rise. The gear may just let you down onto the concrete, or the asphalt, whatever the case. You could yank it up to compensate and then stall and hit harder. Who knows? This situation is filled with all sorts of bad.

[DEX]

Not to derail the thread but if you tried that with the gear handle, there would also be the issue of which gear is of interest to the WOW sensor. On the aircraft I mentioned above, it was the left main gear. So, if you were to try this and somehow the left main gear got unusually light a little early, whether due to a bump or a wind or whatever the case, gear up. But the right main gear and nose wheel are still firmly in the ground! WOW doesn't care. As far as it's concerned, you're airborne.

Now there is the issue of whether or not the hydraulic system for the gear would have the power to force the gear up with that much weight still on the wheels. That would probably depend on the individual design. For instance, is over-center locking used (a passive way of helping to keep the gear down)?

Okay. I'm done. Don't shoot.

[Buckshot]

There is a video somewhere of an SU27 doing exactly that, pilot pulls the gear lever too early, WOW triggers probably due to a small bump or something, SU skids down the rest of the runway.

[Haole]

Lots of different things being said here so hopefully I'll answer the question. The 180 speed isnt unrealistic. For instance...On a "90ish" degree hot summer day in an A/G training configuration (2 tanks, couple of HARMs, heater and Slammer) you will use the following TOLD (Take off and Landing Data)..Rotate at 163, T/O at 178 and that should take about 2600 feet of runway in max AB.
Another thing...when the gear come up so does the flap portion of the flaperons (thats a combo of ailerons and flaps for those of you that dont know). If you raise the gear too soon and those flaperons raise themselves you will lose lift and could settle back down on to the runway. Not pretty!
Hope I answered your question!
Haole

[SUBS17]

I hit the gear switch going down the runway at MIL power so I'd be able to tell the instant weight came off the wheels.

I rotated at 155 and held 10-11 nose up until 169 with no lift. At that point, running out of tarmac, I lit the pipe and the wheels went in transit at 185.

:)
I was refering to this

[Teej]

Lots of different things being said here so hopefully I'll answer the question. The 180 speed isnt unrealistic. For instance...On a "90ish" degree hot summer day in an A/G training configuration (2 tanks, couple of HARMs, heater and Slammer) you will use the following TOLD (Take off and Landing Data)..Rotate at 163, T/O at 178 and that should take about 2600 feet of runway in max AB.
Another thing...when the gear come up so does the flap portion of the flaperons (thats a combo of ailerons and flaps for those of you that dont know). If you raise the gear too soon and those flaperons raise themselves you will lose lift and could settle back down on to the runway. Not pretty!
Hope I answered your question!
Haole

Thanks for the input. Pretty much agrees with what I thought.

Good old density altitude. ;) (hot summer day)

Wonder how bad you'd cringe at my video of landing the overstuffed turkey. :) Over the last 15 seconds prior to touchdown, throttle was built up to MIL with me on final at just over 200 knots with the the FPM centered in the bracket and the nose about 7 degrees up...however, as I started to flare (I was coming in _very_ heavy - normally don't flare with pitch) the stall horn went off. Lit the burner coming over the threshhold for about 2 seconds and went back to MIL as the FPM started climbing. Greased the touchdown at the 2nd hashmarks, nose 13 over horizon at 185 knots. There's a reason you guys don't land 'em this heavy. :)

That was in the SP4.2/BMS2 block 50, 3 tanks 4 * GBU35 + slammers...basically I made the plane about as heavy as I could. Used the burner for about 5 seconds on takeoff...flew 2 miles out then did a 90/270 turn to set up for an approach.

Do let me know if you're ever up in my neck of the woods (Milwaukee). I'll buy you a cold one or two if it fits in the flight schedule.

Teej

[SUBS17]

One thing I'd like to add, Russian aircraft don't feature WOW except Mig29UB. If you throw the switch whilst on the ground the wheels will go up.

[Sun Stealer]

Just checked the vid that Buckshot mentioned. It's a MiG-29 (clean). The gear came up as soon as he'd got his pitch. Not enough speed so it sinks on the pipes. How enbarrassing! :smile: The title is acc-68.mpg

.

[SUBS17]

Thats the reason why the russian aircraft don't have WOW.