F-35B mid-air refuel back ramp C-130 video

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steve2267

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Unread post16 Feb 2017, 14:57

spazsinbad wrote:'steve2267' you probably think I'm not serious however the old NATOPS for the A-4E/F/G has charts (perhaps not so easy to read in PDF format) with explanations about how to calculate fuel usage for every part of a mission from GO to WHOA. The A-4 is single engine and there are two engines cited in the best quality NATOPS I have seen online (I know because I scanned the bastard myself over many many days). Having some insight into the method to calculate fuel usage and being able to compare engines, one can get an insight into the variables noted - altitude, airspeed, weight & drag and suchlike.


Oh, no, I believe you're quite serious. I didn't have an F-35 NATOPS (what is the AF version called? AFTOPS?) or AIM (for us civvie pilots :crazypilot: ) handy, so I got out my napkin and calculator. Was curious to see what sort of hourly fuel flow numbers I'd get and see if they were "reasonable" compared to other aircraft... to see if numnutz solomon et al were full of it. To the first order, the published UK airshow and Japanese deployment numbers appear to show that solomon et al are indeed full of the dark smelly brown stuff, and the F-35 is no worse than any other single engine fighter.

In googling for some information, I found references that most tactical jets liked to refuel between 305-315 KIAS. With Mach 0.95 being 355 KIAS, that would put their refueling speed around M0.85. I "guessed" a cruise speed of M0.8. On Quora, one answerer stated he was an A-10 pilot and that the A-10 refuels at 205 KIAS.

I'm curious if you can probe-and-drogue refuel from a KC-10 / KC-135 @ cruise speed (i.e. M 0.8 ~ 0.85), or if you have to slow down because of the birdie (e.g. bouncing around in the tanker wake).
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Unread post16 Feb 2017, 15:14

I still have not found any reference to IFR speeds for probe-and-drogue ops with KC-10s or KC-135s. Maybe 35aoa or someone can comment.

FWIW, I did find two interesting reads:

Highest Speed / Altitude For Air Refuelling?

Confessions Of A USAF KC-135 'Flying Gas Station' Boom Operator

The first link if the airliners.net forum and in that thread are mentioned numerous airspeeds for IFR off the boom. 315 KIAS seems to be the most common IFR airspeed for tactical aircraft on the boom.
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Unread post16 Feb 2017, 15:54

kc135topboom wrote:
Wingnut767 wrote: (Reply 27):
I have forgotten the speed differences between the boom and the boom with the drogue attached. Was there any? I have noticed that they are developing a high speed drogue now.


There was no speed resriction when the BDA (Boom to Drogue Adapter) was attached. But, IIRC, there was a high drag index that increased fuel comsumption by about 3%-4% (for the KC-135A/Q), for the entire mission.
Source: http://www.airliners.net/forum/viewtopic.php?t=1012621 (Post #29)


Sometimes Tyler has useful information:
The Future Of Aerial Refueling Includes Stabilized Drogues And No Humans
Tyler Rogoway 1/15/15 12:35pm
In the past, different baskets had to be fitted based on what speed the receivers operate at. This means that a KC-130 tanker could not refuel fighters and a loaded down MH-53s in the same mission. This is now changing with companies like Cobham making variable speed baskets. Currently, this is what the company has available when it comes to refueling baskets:

- Low speed VDD: 100-180 kts (Compatible with helicopter and tilt rotor probes)

- High Speed VDD: 180-325 kts (Compatible with NATO STANAG 3447 compliant probes)

- Variable Speed VDD: 105-215kts (Developed for the 48-000 pod on USAF C-130 Aircraft)

Cobham is now working on an all-speed basket that can refuel the whole range of combat aircraft without being changed.

Source: http://foxtrotalpha.jalopnik.com/the-fu ... 1673992575


It appears that probe-and-drogue refueling is viable up to ~325 KIAS (well, I am inferring KIAS).
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Unread post16 Feb 2017, 16:16

Thanks 'StevieWonder' that is interesting (to me) probe/basket info for all speeds improvements indeed. Videos from above RogerAway artickle.



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Unread post16 Feb 2017, 16:53

For giggles and grins, not that it answers my original probe-and-drogue speed question, but at what speed was the F/A-18 refueling in the 2nd video?

It appears to be either 140 kts or 240 kts on the HUD @ 29000 ft. I noted that the tanker's flaperons were slightly extended, which leads me to suspect 140 kts. Of course, they weren't testing airspeed of refueling as much as they were demonstrating / testing / proving automated IFR techniques.
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Unread post16 Feb 2017, 20:42

Again old man brain cells at work .. take it for what it is worth ...

But basket refueling would typically be 240ish KIAS at 25,000 ft max. (350 ish KTAS)
Most assuredly the F-35 (and KC 135/10 for that matter) would have max range cruise closer to 30,000 ft gradually climbing as fuel burns off, at speeds closer to 450-510 KTAS. Dragging across the pond is never at perfect max range cruise conditions for a fighter.

Apart from basket limits (?350Kt/.8M? for High Speed Basket) you need a sweet spot in altitude where there is enough air to maneuver easily (I recall taking a T-38 up over a TStorm to ..... um let`s say "cleared above FL400," and banking threatened stall conditions.The speed needs to be a sweet spot where you can back out and pull in with throttle (without stalling or having to tap AB (which wastes it`s own fuel))

In any case its not at max range cruise speeds or altitudes.

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Unread post16 Feb 2017, 22:22

blindpilot wrote:Again old man brain cells at work .. take it for what it is worth ...

But basket refueling would typically be 240ish KIAS at 25,000 ft. (350 ish KTAS)
Most assuredly the F-35 (and KC 135/10 for that matter) would have max range cruise closer to 30,000 ft gradually climbing as fuel burns off, at speeds closer to 450-510 KTAS. Dragging across the pond is never at perfect max range cruise conditions for a fighter.

FWIW
BP


Thanks, BP! That's for what I was looking!

With a fourship, and if the tanker was equipped with a couple of MPRS pods (one on each wing), then you could re-fuel all four F-35B's in eight minutes or so, accelerate back to cruise (490 kts?) for 50 minutes or so

Yet more revised -B numbers...

Rejiggering the flight from Luke to the UK:
Luke AFB --> RAF Fairford
(3) F-35A's with 18000lb each + 168400 / 3 = 74133 lbs fuel (each)
Flight Time: 4539nm (GC) @ 0.85M (490kts) ~ 9.2 hrs, but land with 5000lb left in the tank.

Fuel Consumption = (74133-5000) / 9.2 = ~7500lb/hr (@ 490kt / 0.85M -- SWAG)

MCAS Yuma --> MCAS Iwakuni
(10) F-35B's each took 766000/10 = 76600 lbs of gas via 25 refuelings = 3064 lbs per hookup.

Assuming every -B gasses up once every 50 minutes, and allowing 10 minutes for passing gas and slowing / accelerating from cruise of 490kts to 350kts IFR speed... And SWAGging a 3 legged route Yuma - Elmendorf - Aleutians - Iwakuni (5662nm) gives a flight time of around 12.1 hours: 10.1 hours @ 490kts (M0.85) and 2 hours refueling @ 350kts (KTAS).

2017_USMC_F-35B_Yuma-Japan_3legs_Aleutians.JPG


If the -B's land with 5000 lbs in their tanks, then their total fuel used will be around 84600lbs.

84600 - 10.1 hrs x 7500lb/hr = 8850 lbs for 2 hours @ 350 KTAS (M0.6) --> 4425 lbs/hr @ M0.61.

But this makes no sense, because I'm tanking once an hour... or about 10 aircraft x 12 hrs = 120 refuelings... and they specifically said 250 IFR ops... So it sounds like they are tanking every half hour. That doesn't leave time to speed up to 490kts and then slow back down again. Also, it was mentioned that the -B's flew with their refueling probes out all the time (!?!) :wtf: And it doesn't make much sense to fly @ 490 KTAS with a refueling probe out... even if it is NOT placarded.

Well, what if they just crawled across the lake via the Aleutians @ 350 KTAS with refueling probes out the whole time?

5662nm @ 350 KTAS = ~16.2 hrs.
Fuel usage: 84600 / 16.2 = ~5230 lbs/hr

Spreading 25 tanking ops per aircraft across 16.2 hrs works out to tanking once every 39 minutes. And if they were getting about 3064 lbs per hookup, and figuring they're keeping their tanks topped up, so they are replacing what they burn every 39 minutes... 3064 / 0.67 hrs = 4728 lbs / hr. This makes more sense to me...

So I am coming up with the following SWAG'd fuel burns:

Cruise @ M0.85 (490 KTAS) ~ 7500lb/hr
Cruise @ M0.6 (350 KTAS) (Basket IFR speed w/ probe out) ~ 4700lbs/hr


Do these numbers make sense to anyone?

Edited: refigured numbers for 350 KTAS instead of 340 KTAS
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Unread post17 Feb 2017, 03:01

Extremely Important Information !!

From Gen Davis this morning before congress.

" Additionally, this redeployment provided valuable lessons-learned as we move forward with the program. For instance, the northern route we took was meant to reduce the number of times the aircraft were required to plug for air-to-air refueling. We have since learned that the fuel models are overly-conservative. Our movement generated data that will be used by the JPO to increase the model’s accuracy."

from http://docs.house.gov/meetings/AS/AS25/ ... 170216.pdf

They spent way too much time low and slow and hanging on the rope.

FWIW
BP

PS @ Steve The tankers use fuel as well. Based on published numbers they would likely cruise at 450-460 KTAS average, not 490. (A/Q`s maybe, but not R`s and 10`s)
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Unread post17 Feb 2017, 05:39

From post #18 of http://www.airliners.net/forum/viewtopic.php?t=1024705 kc135topboom states "but the 'standard' refuel speed was 315 KIAS" which appears to be working out (altitude / temperature / atm pressure dependent) to around M0.8 (~460 KTAS) around 25-30000 MSL.

The Luke - RAF Fairford trip for those three F-35's that went to the UK last year suggests a fuel burn of 7000lb/hr @ M0.8 (460 KTAS).

The three legged Luke - Elmendorf - Adak Island - Iwakuni route is only 347nm longer than the great circle route from Yuma to Iwakuni and it affords numerous divert options out over the Aleutians as seen below. (So I don't know why the good General is deriding to "the north route"... the "north route" is damn close to the great circle route.)

2017_USMC_F-35B_Yuma-Japan_3legs_Aleutians_diverts.JPG


The above figure illustrates several 450nm divert ovals.

5662nm @ 460KTAS --> 12.3 hrs, call it 11 skewer-the-birdies. Fly fifty-five minutes, then replace fuel burned (6416 lbs) in about four-five minutes of swinging on the rope. Worst case leaves 13000 - 6416 = 6584 lbs fuel --> 438nm range @ 1 nm per 15lbs of gas.

Longest leg would be Elmendorf (PAED) to Awakuni (RJOI) of 3469nm. At 460 KTAS cruise, and if a KC-135 burns around 10K lbs / hour (per that airliners.net thread), a -135 would burn on the order of 75000 lbs of JP8. A Killer Bee would burn around 7.54hrs * 7000 lb/hr = 53000lbs. If a -135 can carry 200K lbs of gas, less 75000 for itself and 106000 for two -B's... that leaves 19000 as reserve / extra.

So this napkin calculation suggests one KC-135 could drag two F-35B chicks from Elmendorf to Awakuni @ Mach 0.8 (460 KTAS). This assumes a high speed (315 KIAS) basket for the -135.

Assuming decent weather, figure one day from Yuma to Elmendorf. Enjoy the local nightlife. :shock: Then the next day push to Awakuni. Five tankers each day for ten F-35Bs.
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Unread post17 Feb 2017, 15:10

steve2267 wrote:
So I am coming up with the following SWAG'd fuel burns:

Cruise @ M0.85 (490 KTAS) ~ 7500lb/hr
Cruise @ M0.6 (350 KTAS) (Basket IFR speed w/ probe out) ~ 4700lbs/hr


Do these numbers make sense to anyone?


They are not making sense to me. I think they represent a worst-case, conservative bound. I assumed great circle routes (Hey, you've got TANKERS -- fly a direct GC route!), discounted fuel burn from possibly multiple enroute landings -- and I don't know how many landings they made. I assumed the Luke AFB -> RAF Fairborn trip would give me a decent fuel burn at a decent cruise speed. But 7500lb/hr @ Mach 0.8 (460 KTAS) only leaves a -B with 6000lb in the tank after an hour of cruise, which would be only 368nm "divert" radius, and this ignores fuel burned during climbout. That just sounds too low. Also, the -B is quoted as 900+nm range for a one way trip. But at 7500lb/hr, all 13500lb of gas is gone in 1.8 hrs which, at 460 KTAS is around 828nm. Plus it doesn't leave any gas in the tanks. In a different thread, (viewtopic.php?f=22&t=52826), I learned that since the range is 2X a quoted "mission" radius, and since a mission would seem to require some amount of "reserve" gas in the tank upon RTB, the 900nm range figure must leave some gas in the tanks.

An optimum range cruise speed of M0.8 (460 KTAS) seems a reasonable guess. If one WAGs a guess of landing with 5000lb in the tanks, that leaves a -B with 8500lbs to TO / cruise with. 2 hours cruise would get ~920nm. If you burned 1500 lb for T/O + climb + descent + landing, then 7000/2 = ~3500lb/hr.

Without knowing more, it would seem the cruise burn for an F-35 is somewhere between 3500 lb/hr and 7500 lb/hr. Quite a large margin, and that high figure seems really high, but I cannot reconcile it with the Luke - Fairborn quoted IFR numbers, as I don't know actual flight times, route, #stops etc.
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Unread post20 Feb 2017, 05:10

Mebbe THERE WILL BE SOMETHING NEW in this article & Mebbe it will be freed sometime soon [JUST A REPEAT from 14th?]

viewtopic.php?f=61&t=27157&p=362822&hilit=Seligman#p362822 [14th Feb Arstickle]
Are U.S. F-35s Refueling Too Often?
20 Feb 2017 Lara Seligman

"A recent, lengthy journey by U.S. Marine Corps F-35Bs from Arizona to Japan has sparked a quiet debate within the Pentagon about how often the stealthy fighter needs to refuel during ocean crossings. It took seven days for 10 U.S. Marine Corps F-35Bs to fly from Yuma to their new home at Iwakuni, Japan, a flight that on a commercial airliner normally takes less than 24 hr. Many factors contribute to the time it takes a military fighter to get from point A to point B: weather, terrain and ..."

Source: http://aviationweek.com/combat-aircraft ... -too-often
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Unread post20 Feb 2017, 16:07

The above article has gone from the list but remains at the URL - likely it is just a repeat from AvWEAK - the old codgers.

NOW this is at the opening list of articles - but click on the link and youse get the one above - did I say OLD CODGERS!? :mrgreen: Theys linked to an improper article.
Are U.S. F-35s Refueling Too Often? 20 Feb 2017
"The Air Force requires the fighters to hit the tanker every 30-40 min. during an ocean crossing....More"
http://aviationweek.com/combat-aircraft ... -too-often
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