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J Model Performance Specs


Spectre623
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Been reading the Air Force Association 2013 USAF Almanac on the J Model performance. It says The range with 35000 lb payload is 1,841 miles and the J-30 with same payload, range is 2,417 miles. Where do they pick up 576 more miles of range with the same amount of fuel and engines but dragging the weight of 15 more feet of aluminum around? By the way who does the TOLD card on the J. He would know...right ? Bill

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You are correct that the J-30 has a higher empty weight (about 4,000 lb), but it also has a higher max takeoff gross weight (164,000 lb vs. 155,000 lb for the J). That means about an extra 5,000 lb of fuel for the J-30 with the same payload.

With no FE, the pilots do the TOLD card...if at all. TOLD calcs are done on the Mission Computer based on input for the pilots.

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Does the J-30 have a different tank lay out and capacity than the standard J, which I thought had the same tanks as the E and H? Are you saying the difference is the J don't use externals and the J-30 does? If so I can see where the -30 would get the extra mileage. Bill

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Both the J and J-30 have the same fuel tank layout and roughly the same volume as the Es and Hs (some volume is displaced by explosive suppressant foam). They both have provisions for externals, but the baseline configuration is without externals, which I assume is what the Almanac data are based on.

When carrying 35,000 lb payload, the max takeoff weight limit (155,000 lb) is reached before the tanks are full on the J. However, the max takeoff weight of the J-30 is higher (164,000 lb) so it can put more fuel in the tanks with the same payload, even after accounting for the higher empty weight.

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As I recall, the C Mk3 is a stretch H, so it has that in common with the J-30 (or C Mk4 in RAF jargon). The RAF birds have always been a little different. Maybe their engineering organization cleared the Mk3 beyond Lockheed's limits...

I considered them stretched Super-Es - most were '68 vintage. My point was they were cleared to the same basic weight limits as the J-30. However, they didn't use a dash-1 for guidance like the majority of Air Forces do, they wrote their own guidance based primarily on the FAA type certificate for the L100/L382...which meant they were often more restrictive. Make no mistake, they picked and chose which things to use in their book, but it was decidedly a mish-mash between T.O. and FAA Type Certificate standards.

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The RAF Mk.3 was the same - normal max gross weight was around 163K, but emergency wartime weight was still 175K (of course, they did it in kilos)

Ernie,

Well, here I go hijacking a thread again.

You mentioned the weights were in kilos. Were the fuel gauges in kilos, too? The reason I ask is that Transafrik had a 727 with the fuel gauges in kilos. It was a real panic attack when you'd look down at the gauges and momentarily think you were almost out of gas!

OK, back to the original thread.

Don R.

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US Herk, I'm familiar with the RAF tech pubs - completely different from all other operators. They have their own Aircrew Manual (-1 of sorts) and Operating Data Manuals (ODM) for performance. Since the RAF was the launch customer for the J, they levied a requirement that it be FAA/JAA certified. That explains a lot of the civil limits and procedures in the books.

DC10FE, All of the fuel quantity values in the RAF J ODM are in kilos, so I assume that the gauges are also in kilos. The conversions always screwed me up but you get used to it after a while.

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Ernie,

Well, here I go hijacking a thread again.

You mentioned the weights were in kilos. Were the fuel gauges in kilos, too? The reason I ask is that Transafrik had a 727 with the fuel gauges in kilos. It was a real panic attack when you'd look down at the gauges and momentarily think you were almost out of gas!

OK, back to the original thread.

Don R.

Yep, fuel gauges in kilos. That was relatively knew on the fleet when I showed up in '00. Going from kilos to pounds was easy, (KGx2 + 10%), but the other way was slightly trickier. ;) Had that same momentary panic attack too...that and the gauges didn't move as quickly, so I often wondered if they were stuck or broken. ;)

US Herk, I'm familiar with the RAF tech pubs - completely different from all other operators. They have their own Aircrew Manual (-1 of sorts) and Operating Data Manuals (ODM) for performance. Since the RAF was the launch customer for the J, they levied a requirement that it be FAA/JAA certified. That explains a lot of the civil limits and procedures in the books.

.

I was referring to their K-model books, but no doubt their J-model books are the same. It was just really starting to be used in '00-01 when I was there. 24 SQ was just starting to do operational route flying (airland trashhaul) - there was no tac being done outside of the their test squadron at the time.
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