Forum: Program and politics

Pentagon Slackens Difficult-To-Achieve JSF Performance Requirements
Inside Defense (subscription)

"DefenseAlert, March 1, 2012 -- The Pentagon last month relaxed the performance requirements for the Joint Strike Fighter, allowing the Air Force F-35A variant to exceed its previous combat radius -- a benchmark it previously missed -- and granting the Marine Corps F-35B nearly 10 percent additional runway length for short take-offs, according to Defense Department sources."

http://insidedefense.com/

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What KPP could it relax in order to get MORE range out of a F-35A?

Anyone with a InsideDefense.com subscription care to post the whole thing (or at least give details)?

Perhaps decrease the minimum required fuel reserves, allowing more fuel to be spent on range?

HV

Or they included the SDD 5% reserve?

SpudmanWP wrote:

What KPP could it relax in order to get MORE range out of a F-35A?

Anyone with a InsideDefense.com subscription care to post the whole thing (or at least give details)?

From the article:

Quote:

Sources familiar with the changes, however, said the JROC -- which also includes the service vice chiefs of staff -- agreed to adjust the "ground rules and assumptions" underlying the F-35A's 590-nautical-mile, combat-radius KPP.

Quote:

To extend the F-35A's combat radius, the JROC agreed to a less-demanding flight profile that assumes near-ideal cruise altitude and airspeed, factors that permit more efficient fuel consumption. This would allow the estimate to be extended to 613 nautical miles, according to sources familiar with the revised requirement.

In relation to the F-35B STOVL variant, the allowable short takeoff distance is being changed from 550 feet to 600 feet.

Quote:

The JROC, accordingly, agreed to extend the required take-off distance to 600 feet, according to DOD officials.

Those are the only KPP changes mentioned in that article.

Thanks for amended KPP info 'Conan'.

[sarcasm]WOW... 613 miles versus 590 miles for a combat jet fighter, and an extra 50 feet of runway for STO...[\sarcasm]

So we're talking the difference between a headwind or tail wind?

Do these KPPs account for other factors like Cold vs Hot performance? or High altitude airfield operations? (both of which could make/break the KPPs either way)

Not to mention ANYTHING that is 'established' for range can be made or broken by flying style. IE how 'heavy' one's hand is on the throttle. Most pilots can tell you how to squeeze extra range from a jet.

Don't get me started on the STO's 50 feet. Try the 600 foot takeoff in Kuwait when it's 120+ and you can see the humidity versus performing the same at Minot when it's 10 below.

Glad someone made a mountain out of this mole-hill. Doh

TEG

Salute!

Still laughing, TEG.

I can personally vouch that pilot technique can easily extend or detract from the "theoretical" range. Outlaw can do the same.

OTOH, sometimes just 1,000 pounds of ordnance or gas can make a difference. Or, give me a longer runway.

- In the Viper, we didn't practice on a regular basis with a decent loadout of bombs, not did we zip around at a high airspeed. So when we got to Red Flag and carried 6 or 8 eggs and pods and....., we had to use those big wing tanks. Nevertheless, we could go pretty far at 540 knots on the deck at 90% rpm or so. Figure hour and a half without reducing power when RTB, or climbing after out of the threat area. A longer runway could allow a mil power takeoff and save a few hundred pounds of gas.

- The SLUF was a different story, and TEG's comments about altitude, humidity and temperature is right on. We had practiced with no external tanks or real bombs without a problem. Then we deployed to Korat and temps were in the 40 deg C range and we carried 10 x 500 or 6 x 1000 eggs and the external tanks.

Talk about exciting takeoffs! Would roll to the other end of the runway and pull the sucker off and stagger up until gear and flaps were up, then slowly accelerate to climb speed. Some guys even bounced off the overrun because they yanked too hard or too much AoA. Believe this! We dropped 2 x 500 eggs from the load whenever "computed" takeoff was more than 85% of the runway. No kidding. Still a very long roll and we had three check speeds, plus we turned off the airconditioning system to get another few pounds of thrust.

What that did for us was give us the same range and "hang time" at the target even tho we had less eggs.

We also learned to grab for altitude soon as outta the target area and cruise at a slower speed/lower power setting.

+++++++++++++

So I can see that a few tweaks of the spec could make a difference, considering USAF and LM are prolly using some "model" to fly the profile. I also agree with TEG that pilot skill and cunning could make up for the difference.

Gums sends...

Free Version Page has this to say now: 04 March 2012

Pentagon Slackens Difficult-To-Achieve JSF Performance Requirements
Posted on InsideDefense.com: March 1, 2012

http://insidedefense.com/20120301239200 ... d-926.html

"...The short-take-off-and-landing KPP before the JROC review last month was 550 feet. In April 2011, the Pentagon estimated that the STOVL variant could execute a short take-off in 544 feet while carrying two Joint Direct Attack Munitions and two AIM-120 missiles internally, as well as enough fuel to fly 450 nautical miles. By last month, that take-off distance estimate grew to 568 feet, according to DOD sources.

The JROC, accordingly, agreed to extend the required take-off distance to 600 feet, according to DOD officials...."

"The JROC review of the F-35 program last month was held in accordance with a policy adopted by the council in June 2010, which requires a reassessment of requirements for all programs with cost growth exceeding 25 percent of the original program baseline. One goal of the policy is to determine whether a decision to relax requirements should be made to improve acquisition cost and schedule estimates."

The F-35A was only short of it KPP for radius of a few nms and the deficiency had been known for a while. There was talk of enlarging or adding a fuel tank, but a minor adjustment to a KPP seems to be a more prudent approach in this case - why spend a ton of money to achieve a marginal increase in range, with the possibility creating other problems (COG, W & B, GTOW, etc.) Also, these range values are still estimates.

The F-35B KPP adjustment is a bit of a surprise, and is probably indicative of a weight increase on an aircraft that has little room for weight growth. They built in a tiny margin to allow for further weight growth in the revised KPP, but there is only so much runway on a LHA on a hot day in the WestPac for instance. Something to watch.

http://insidedefense.com/20120301239200 ... d-926.html

maus92 said or quoted?: "...there is only so much runway on a LHA on a hot day in the WestPac for instance...." At least this short runway can turn into the wind and accelerate - then the wind chill factor kicks in also. Very Happy

spazsinbad wrote:

maus92 said or quoted?: "...there is only so much runway on a LHA on a hot day in the WestPac for instance...." At least this short runway can turn into the wind and accelerate - then the wind chill factor kicks in also. Very Happy

Or maybe this was already considered when calculating the original KPP.

This WOD factor is mentioned in an old PDF about such matters but not mentioned above in your 'hot day in WestPac' comment. Why not?

SpudmanWP wrote:

What KPP could it relax in order to get MORE range out of a F-35A?

Anyone with a InsideDefense.com subscription care to post the whole thing (or at least give details)?

They didn't relax the KPP, they altered the GR&A which allowed the aircraft to fly at optimum altitude vice an arbitrary number. There are other elements of the GR&A which were not changed and they remain very conservative by legacy standards.

Here is the old KPP mentioned with WOD criteria. Don't know if this Environmental Condition applies today but it is notable that 'tropical' is mentioned. BUT does this include WestPac? Are they in the Tropics? Quote below is mentioned elsewhere on this forum probably multiple times by now BTW.

Scorecard: A Case study of the Joint Strike Fighter Program by Geoffrey P. Bowman, LCDR, USN — 2008 April

http://www.f-16.net/f-16_forum_download-id-14791.html [PDF 0.3Mb]

"The USMC has added STOVL performance as a service specific key performance parameter. The requirement is listed as follows: With two 1000# JDAMs and two internal AIM-120s, full expendables, execute a 550 foot (450 UK STOVL) STO from LHA, LHD, and aircraft carriers (sea level, tropical day, 10 kts operational WOD) and with a combat radius of 450 nm (STOVL profile). Also must perform STOVL vertical landing with two 1000# JDAMs and two internal AIM-120s, full expendables, and fuel to fly the STOVL Recovery profile.

The Marine Corps has used the more limiting deck launch, rather than a simple expeditionary airfield, to frame its requirement."

Forum: Program and politics

KPPs being adjusted for F-35A & F-35B