Acceleration

Discuss the F-35 Lightning II
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Unread post27 Nov 2016, 21:55

Salute!

Thread is bout accel, and I have flown two jets with awesome accel. Nevertheless, the total capabilities of the weapon system and the envisioned threat needs to be considered.

The Viper accelerated about like the VooDoo I flew back in the mid-sixties. Imagine unloading at 20K and 0.9M in a 20 - 30 deg climb, then passing the mach still climbing and getting to 1.33M about when reaching level and then back up to 50,000 freeking feet in another minute and a half or so. That was our climb schedule back in 1966. In the Viper I would have my solo stud ( clean A model) start at 400 KIAS and then light burner and do a 90 deg turn pulling 3 gees and roll out. So at 5,000 feet he would wind up at about 700 knots and 1.1M or so.

Accel is great in and of itself, and the Stubbie without external stores is gonna be as good as the Raptor. Remember that the Viper is drag limited a lot more than weight limited. It was very obvious to us in those early days when we flew with those huge wing tanks, and the centerline not so much.

Slightly off topic but I gotta go with Steve. Sorry Count. So from Steve:

Take an F-16, stir in a little A-7, bake, then sprinkle on a generous helping of F-117. What do you get? An F-35.


To be honest, adding the A-7D to the mix is one good thing to consider. As a SLUF/Viper dude I feel well-qualified to speak from the peanut gallery. Thing to remember is it was veeeery slugish and had a huge RCS. Nevertheless, it remained the permier bomb truck until the early 80's.

The F-35 is more like the SLUF WRT avionics/nav/sensors. Especially the nav. Biggest difference is the neat radar - AESA, isn't it? Our SLUF dar was really good for A2G and terrain following/avoidance and such. The Viper DAR was good A2G without TF or TA modes, but that was all. A2A radar in the Viper was like an Eagle or Hornet ( only had a few dozen hours in those sims, but the avionics were accurate if not the aero, ditto for the F-20 sim).

@Count

Talk to any Viper pilot that flew the SLUF first. Ditto for Double Ugly folks that came to we lowly mudbeaters in the SLUF.

Our SA was way beyond anything else we had flying in the tactical environment except the 'vaark. We had super radar for ground map, TF and TA and beacon-bombing. We had a great INS with a doppler system, so we could takeoff with a 2 nin alignment and then do an airborne INS alignment using that doppler. Or we could go pure doppler or pure INS or another two mixed modes. Neat huh? And then the biggest bonus - the projected map display.

see the attached PMDS article from the Fighter Weapons Review. It was the template for my address to the DMA folks at the St Louis facility that produced our maps on 35 mm film for our gizmo. No kidding. I got to meet the gnomes that did all the good work.

The two biggest fears of a fighter/attack pilot is running outta gas and knowing where you are. In the SLUF we had all bases covered, but getting away from the enema in A2A was a problem, heh heh.
++++++++

I like the overall F-35 implementation now. It is not a bomb truck like the SLUF or Bone or Buff. But the sucker will likely get in and hit and get out. It will also help other friendly folks. I would like to try it myself.

Hope all had a great Thanksgiving here in the states and across the world, holiday or not.

Gums opines...
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Unread post23 Jul 2019, 10:42

Perhaps, I Excavation, dug up the Questions that everyone is also secretly interested in. 8) (I'm a digging Man.)
https://www.instagram.com/stories/highl ... 094008342/ (This is a DEMO team account.)
We have F-35 crew chief Staff Sgt John Baker here to answer your questions.

Q: what's the best part of the F-35 to you and what is the best part of flying it.
A: The best part of the F-35 is the engine!

Q: What mach number does the F-35 go up to.
A: Top speed is 1.6 Mach!

Q: Is it true that the F-35's acceleration is very comparable to the F-22's?
A: Very comparable.

The F-35 has the largest single engine motor out of any fighter (43,000lbs of thrust)
The F-22 is a twin engine fighter with 70,000 lbs of thrust.
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Unread post24 Jul 2019, 19:24

"The F-35 doesn’t have the altitude, doesn’t have the speed [of the F-22],
but it can beat the F-22 in stealth,” Hostage told me

Acceleration times from Mach 0.8 to Mach 1.2 were extended by eight seconds, 16 seconds
and 43 seconds for the A, B and C-models respectively. The baseline standard used for the
comparison was a clean Lockheed F-16 Block 50 with two wingtip Raytheon AIM-120 AMRAAMs.

1. Acceleration may be on part with an F-22, but even my pickup truck can beat either
jet 0-60mph. You can twist things around if you want to get the desired shock and awe
affect of a public comment on acceleration. Acceleration is great until you run out speed.

2. Per the above, acceleration is being compared to a dirty F-16 and not clean as people
here always suggest. I know they call it clean, but being loaded with 2 amraams isn't
by definition clean. Yes, drag is small on the amraam.
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Unread post24 Jul 2019, 19:35

wooster wrote: I know they call it clean, but being loaded with 2 amraams isn't
by definition clean. Yes, drag is small on the amraam.


Do you honestly think it's enough to care about?
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Unread post24 Jul 2019, 19:52

According to the FM, wingtip AIM-120Bs have a DI of 0. Still a clean aircraft.
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Unread post25 Jul 2019, 06:23

wooster wrote:1. Acceleration may be on part with an F-22, but even my pickup truck can beat either
jet 0-60mph. You can twist things around if you want to get the desired shock and awe
affect of a public comment on acceleration. Acceleration is great until you run out speed.


But who needs more air speed than that?

>1.6 = more heat = much higher fuel burn rate = seriously reduced range = much less useful

Speed mattered when "Speed is Life" = 3rd and 4th gen thinking

5th-gen = "Not Being Tracked is Life" = If you are not seen then high speed does not even matter much.

Acceleration, to a useful speed, is more important to getting somewhere fast, and then being still able to dominate the air and loiter when you arrive. The fight is mostly transonic, where unseen high acceleration is the most important ability after agile turning.

Or ... Accel + Alt + VLO + DAS + MDF + Radial Distance = LIFE . . . Always choose Stealth
Accel + Alt + VLO + DAS + MDF + Radial Distance = LIFE . . . Always choose Stealth
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Unread post25 Jul 2019, 23:19

sprstdlyscottsmn wrote:According to the FM, wingtip AIM-120Bs have a DI of 0. Still a clean aircraft.


That's because the baseline DI = 0 for F-16 includes wing tip missiles. DI is the incremental drag effect of external stores above a defined baseline. Of course the drag effect of tip missiles is very small, as you say. One reason the effect is small is the launcher and missile combine to increase the aspect ratio, which generally reduces the AoA a tiny amount, for less induced drag.

Drag Index is based on 1g flight at 0.80 mach. It is not intended to provide accurate drag increments at all conditions, but is intended to help estimate cruise range for various store loadings.
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Unread post25 Jul 2019, 23:22

johnwill wrote:That's because the baseline DI = 0 for F-16 includes wing tip missiles. DI is the incremental drag effect of external stores above a defined baseline. Of course the drag effect of tip missiles is very small, as you say. One reason the effect is small is the launcher and missile combine to increase the aspect ratio, which generally reduces the AoA a tiny amount, for less induced drag.

Drag Index is based on 1g flight at 0.80 mach. It is not intended to provide accurate drag increments at all conditions, but is intended to help estimate cruise range for various store loadings.

Right, while not physically clean the FM considers tip missiles to be part of a Basic Airframe.
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Unread post26 Jul 2019, 04:00

sprstdlyscottsmn wrote:
johnwill wrote:That's because the baseline DI = 0 for F-16 includes wing tip missiles. DI is the incremental drag effect of external stores above a defined baseline. Of course the drag effect of tip missiles is very small, as you say. One reason the effect is small is the launcher and missile combine to increase the aspect ratio, which generally reduces the AoA a tiny amount, for less induced drag.

Drag Index is based on 1g flight at 0.80 mach. It is not intended to provide accurate drag increments at all conditions, but is intended to help estimate cruise range for various store loadings.

Right, while not physically clean the FM considers tip missiles to be part of a Basic Airframe.


I believe its also a balance issue for the Viper.
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Unread post26 Jul 2019, 17:27

It flies fine without them, but they do help with flutter and wing bending moments with the AIM-120 helping more than the AIM-9. This is why the AIM-120 is always on the wingtips while the AIM-9 is on the outboard pylon.
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Unread post26 Jul 2019, 21:54

The structural design of the launcher / tip area is controlled by the abrupt twanging (sorry, technical term) the missile gets while ejecting a 2000 lb bomb from station 3 or 7 in a 4g pullup. The loads and stresses in that condition are much higher than any 9g turn or 6g roll.

Another severe case is jettisoning a 370 tank at 1.6 mach. The shock waves from the tank sweep over the missile, launcher, and tip as the tank pivots downward and falls away. It was checked in flight test, but I don't know if it ever has happened in service.
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Unread post26 Jul 2019, 22:12

:notworthy:
johnwill wrote:The structural design of the launcher / tip area is controlled by the abrupt twanging (sorry, technical term) the missile gets while ejecting a 2000 lb bomb from station 3 or 7 in a 4g pullup. The loads and stresses in that condition are much higher than any 9g turn or 6g roll.

Another severe case is jettisoning a 370 tank at 1.6 mach. The shock waves from the tank sweep over the missile, launcher, and tip as the tank pivots downward and falls away. It was checked in flight test, but I don't know if it ever has happened in service.

:notworthy:
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Unread post27 Jul 2019, 07:38

element1loop wrote:
Speed mattered when "Speed is Life" = 3rd and 4th gen thinking

5th-gen = "Not Being Tracked is Life" = If you are not seen then high speed does not even matter much.



I cant remember where I read or heard it but it was from an F-22 pilot talking about their experience in the F-22. It went something along thr line of...
Flying above 50000 feet supercruising close to mach 2 and being stealthy, I can see everything but no one and nothing can touch me. I can give someone a bad day without knowing I was there and be on my way out before they even know what is going on.


Stealth and SA are a must in the world of 5th gen capabilities but having speed is indeed a bonus...

https://fas.org/man/dod-101/sys/ac/docs ... 991378.htm

Its ability to supercruise will allow the F-22 larger patrol areas, and permit the Raptor to enter and exit hostile areas in quick fashion, reducing the time a pilot spends over an enemy's territory," he said. "The capabilities of an F-22 aircraft will be a great benefit to our warfighters.


Flying fast in terms of the F-22 also means that they use less fuel...
https://www.safie.hq.af.mil/Portals/78/ ... 154531-787
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Unread post27 Jul 2019, 08:54

charlielima223 wrote:
charlielima223 wrote:...Flying fast in terms of the F-22 also means that they use less fuel...
https://www.safie.hq.af.mil/Portals/78/ ... 154531-787

This PDF illustrates flying 'slightly faster' during CORONET MISSIONS (when ARF x many times is carried out) does not imply flying faster generally means 'fuel is saved'. One would have to have the DASH ONE/NATOPS figures to work this out OK.
"...FLY FAST, SAVE GAS?
Two F-22 CORONET demonstrations showed flying at a faster airspeed, including during air refueling, not only reduces transit time, but also saves fuel. In January 2014, Maj Sterling Boyer and Mr. Don Reese, working with TACC and the AOS, developed the concept of flying and air refueling F-22 CORONETs at 335 KIAS, closer to F-22 maximum range airspeed and within boom limits, instead of the standard 310 KIAS. The first demonstration flew 12 F-22s with KC-10 and KC-135 tanker support from Langley to Hickam, then on to Kadena, measuring a range of factors including fuel use, flight hours, and aircraft stability. Results indicated significant savings not only in flight time, but also net fuel, which could have a large impact if the method is applied across the fleet...."
RAN FAA A4G Skyhawk 1970s: https://www.faaaa.asn.au/spazsinbad-a4g/ AND https://www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/
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Unread post27 Jul 2019, 16:37

In Speed vs. Stealth, if indeed they are at odds with each other, Stealth wins at any speed point.
https://elementsofpower.blogspot.com/20 ... -wins.html
--The ultimate weapon is the mind of man.
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