Max Q
Topic Author
Posts: 6811
Joined: Wed May 09, 2001 12:40 pm

In flight refueling to over MGTOW

Thu Nov 08, 2018 6:12 am

I was just reading an article by an
Air Force boom operator on a KC135


He stated they offloaded so much
fuel to a C5 that the Galaxy’s ‘in flight
weight’ exceeded one million pounds


This was to allow it to fly non stop from
Afghanistan to the west coast of the US


Couple of things, I think it’s possible that
certain military aircraft are permitted a higher in flight weight than MGTOW after
in flight refueling ?



But I would think over a million pounds on a C5 seems excessive and overstress the airframe ?
The best contribution to safety is a competent Pilot.
 
WIederling
Posts: 6835
Joined: Sun Sep 13, 2015 2:15 pm

Re: In flight refueling to over MGTOW

Thu Nov 08, 2018 9:52 am

I've seen a couple of "overrefuel" stories mentioned here over time.
( though not C5 more related to B-52 )

i.e. get the plane off the ground and then fill up to full tanks.
( MTOW stands for Max Take Off Weight :-)
Murphy is an optimist
 
GalaxyFlyer
Posts: 1495
Joined: Fri Jan 01, 2016 4:44 am

Re: In flight refueling to over MGTOW

Thu Nov 08, 2018 2:57 pm

The C-5A/B emergency war in-flight gross weight was 840,000 pounds. It was occasionally waivered for peace time missions that couldn’t be accomplished otherwise. When they hauled the DSRV out to HI when the USN sub struck and sank the tour boat, I think they were waivers. I planned a trip carrying the Mark V SOC boat ex-Townsville that required an EWO waiver. The problem leg was Andersen to Hickam, not getting the waiver would have required a tech stop for both tanker and C-5. Took some persuading but granted.

Considering the city-pairs and M models can make the East Coast non-stop, depending on load, without AR, I suspect, it was not anything like that. OEW is about 396,000, max fuel is about 325,00, so full fuel TOW is about 721,000 leaving a 119,000 pound payload, about right for 36 pallets. An AR coming off the NATs or over Canada would work.

A million pounds is a little hard to believe as 903,000 I think was the record and you’d be refueling in the low to mid-teens. The M has 840,000 as the standard MTOW.


GF
 
mmo
Posts: 1637
Joined: Thu Apr 18, 2013 3:04 pm

Re: In flight refueling to over MGTOW

Thu Nov 08, 2018 7:50 pm

Back in the early 80s, The B-52D was tested for a max inflight weight. MTOW was 450,000 (G/H 488,000) but on the D with a full load internally and both pylons full you were not even close to full tanks. IIRC the capacity was around 250,000 lbs and I think we ended up at about 550,000 inflight. We also upped the refuelling airspeed from 255 to 280 which put the aircraft on the good side of the power curve, but it was a real pig. Could barely hold on with 7 engines.
If we weren't all crazy we'd all go insane!
 
GalaxyFlyer
Posts: 1495
Joined: Fri Jan 01, 2016 4:44 am

Re: In flight refueling to over MGTOW

Thu Nov 08, 2018 8:20 pm

The dreaded 7-engine refueling.

While C-5 performance was dreadful at EWO, we practiced take-off and emergency OEI returns in the sim. At standard day, I think the MTOW achievable was about 809,000. The OEI approach was similar to a two-engine approach, gear first, flaps 40% at G/S capture, speeds were high.

GF
 
Max Q
Topic Author
Posts: 6811
Joined: Wed May 09, 2001 12:40 pm

Re: In flight refueling to over MGTOW

Thu Nov 08, 2018 11:57 pm

Thanks for the replies

Just to be clear, do any military aircraft have a permitted inflight weight above normal MGTOW after inflight refueling


If so is this often done ?
The best contribution to safety is a competent Pilot.
 
GalaxyFlyer
Posts: 1495
Joined: Fri Jan 01, 2016 4:44 am

Re: In flight refueling to over MGTOW

Fri Nov 09, 2018 12:03 am

Yes, the C-5A/B did, by HQ waiver for mission accomplishment. With the waiver, one could go from normal T/O weight of 769,000 to 840,000 inflight only. Not frequently, AR is often too expensive unless high priority mission. The M just operates to 840,000.

GF
 
Max Q
Topic Author
Posts: 6811
Joined: Wed May 09, 2001 12:40 pm

Re: In flight refueling to over MGTOW

Fri Nov 09, 2018 12:14 am

GalaxyFlyer wrote:
Yes, the C-5A/B did, by HQ waiver for mission accomplishment. With the waiver, one could go from normal T/O weight of 769,000 to 840,000 inflight only. Not frequently, AR is often too expensive unless high priority mission. The M just operates to 840,000.

GF




Thanks, interesting, that’s a significant increase in weight once airborne
The best contribution to safety is a competent Pilot.
 
GalaxyFlyer
Posts: 1495
Joined: Fri Jan 01, 2016 4:44 am

Re: In flight refueling to over MGTOW

Fri Nov 09, 2018 1:08 am

Lots of military planes have EWO weights for wartime missions, but they involve more damage cycles and performance restrictions. As I said, a C-5 couldn’t met take-off perf at EWO weights. Formatting behind the tanker was also a performance limit, 800,000 pounds would probably have a max altitude of F200.

In my example, the C-5 and the tanker would have had to tech stop at Wake Island and possibly Midway, if the waiver wasn’t granted. Often, we could work around it by careful planning of the tracks or ALTREVs, but Guam-Hawaii with a 250,000 payload and only about 4 hours of fuel made it hard.

GF
 
JohnM
Posts: 391
Joined: Sat Feb 24, 2001 12:35 pm

Re: In flight refueling to over MGTOW

Fri Nov 09, 2018 7:49 pm

Another issue is when FRED has a high fuel load, expect fuel leaks from the extended range tanks. The ER tanks don't see high fuel levels very often, so expect leaks. I don't think it would be a huge issue in flight, but sitting on the ground like that, be prepared to see some puddles around the airplane, and the hassles with that.
 
GalaxyFlyer
Posts: 1495
Joined: Fri Jan 01, 2016 4:44 am

Re: In flight refueling to over MGTOW

Fri Nov 09, 2018 8:39 pm

True enough!

Who is online

Users browsing this forum: ITMercure and 26 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos