Forum: General F-35 Forum

Last edited by cywolf32 on Aug 27, 2012 - 08:06 AM; edited 2 times in total

Sorry Spud,

I read it back and now feel ignorant. It's just the nitpicking discussions drive me silly sometimes regarding this program. The Internet allows great debate, but ludicrous discussion as well. My bad.

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np, we all have our moments Wink

The weight margins: Are they absolute, as in can't ever exceed until engine thrust is increased, or do they take into account additions being added to the aircraft later?
While gathering reference images for modelling I noticed that an early photo of a wind tunnel model shows a lot of extra weight attached near the landing gear doors.

cywolf32 wrote:

fire suppresion systems are common hardware on ANY AIRCRAFT built regardless of type built in the US. your ignorance for such matters shows quite well. anyone who has worked fighters would know the weight penalty is negligent in terms of what it offers of safety to the pilot and acft.

Yah.

Aircraft, especially combat aircraft, have fire suppression systems. Typically in the engine and avionics bays at least, not spread throughout the airframe as Spudman was saying.

That said Spudman may have forgotten this:

Quote:

TESTIMONY OF DR. J. MICHAEL GILMORE DIRECTOR, OPERATIONAL TEST AND EVALUATION OFFICE OF THE SECRETARY OF DEFENSE
BEFORE THE UNITED STATES HOUSE ARMED SERVICES COMMITTEE March 24, 2010

http://armedservices.house.gov/pdfs/Joi ... 032410.pdf (81Kb)

"...I want to briefly highlight a system vulnerability issue included in my Annual Report. The program office is executing a comprehensive, robust, and fully funded Live Fire test plan. However, the program’s removal of shutoff fuses for engine fueldraulics lines, coupled with the prior removal of dry bay fire extinguishers, has increased the likelihood of aircraft combat losses from ballistic threat induced fires. F-35 live fire testing to date has shown that threat impact into fuel tanks results in sustained fires. In addition, the F-35 will be more vulnerable to typical non-combat fires caused by fuel leaks and other system failures without the fire-suppression systems. At present, only the Integrated Power Plant (IPP) bay has a fire suppression system. Though the configuration control process has approved the program office’s request to remove these safety systems as an acceptable system trade to balance weight, cost, and risk, I remain concerned regarding the aircraft’s vulnerability to threat-induced and safety-related fires."

Now that’s older news and they may have replaced the system at this point with a lighter more expensive fire suppression solution, but a lot of the fire suppression systems were removed to save weight and cost which sort of argues pretty strongly against your “weight penalty is negligent in terms of what it offers of safety to the pilot and acft” statement.

A better answer to why it might(?) have fire suppression systems spread throughout the airframe would have been to point out that the F35 utilizes a "fueldraulics" system which almost certainly adds a couple of large fire risks to the aircraft.

:: Edited by moderator - Insults removed, poster warned. ::

In part answer to 'munny' question above: "...The weight margins: Are they absolute, as in can't ever exceed until engine thrust is increased, or do they take into account additions being added to the aircraft later?..." As indicated by the USMC Commandant the weight margins for F-35B have increased by various methods most likely, with apparently some extra positive margin due to how these things are calculated + engine performance as shown below.

In the F-35B case there is an absolute weight limit (for VLs) and also for the F-35C within other parameters for arrested landings, where the max. landing weight/ Optimum Angle of Attack Airspeed is a limit for the arrestor gear and aircraft under the worst circumstances. However there would be some flexibility margins. As shown in a recent entry in the Lakewood arrest test facility Super Hornets were very well tested for carrier landings etc. And I would guess the same applies to future F-35C testing at weights over the KPP limit. Already drop tests have proved some limits etc.

What a 'not to exceed' weight limit would be for the F-35A I don't know as apparently discussed on the forum earlier it is likely that the aircraft can land at any weight that does not exceed the maximum tyre ground speed AFAIK this is 170 knots.

And there would be a lot more to this I guess but that'll do from me at moment.

PARLIAMENTARY JOINT COMMITTEE ON FOREIGN AFFAIRS, DEFENCE & TRADE
Department of Defence annual report 2010-11 | 20 MARCH 2012

http://parlinfo.aph.gov.au/parlInfo/dow ... 70/0000%22

"...[Burbage] Today, all the KPPs are green because that ground rule was changed to be common across all three airplanes on the range. But we have not taken back the margins that are being withheld to make sure those performance predictions are conservative. We are not going to have degraded engines. We basically measure our performance characteristics with a highly-degraded engine capability. Our actual flight test information coming back from the engine is better than nominal. These calculations are not done using actual airplane test data. They are done using an artificial penalty that gets paid back as the design matures....”
__________

F-35B starts critical tests in comeback attempt Stephen Trimble 05 Oct 2011

http://www.flightglobal.com/news/articl ... pt-362941/

"...Meanwhile, programme officials also appear to have resolved a 90.7kg performance shortfall in the vertical lift bring-back weight of the F-35B in hover while returning to a ship. Engine manufacturer Pratt & Whitney has confirmed the solution includes raising the output of the propulsion system by about 100lb-thrust (0.4kN)...."

Forum: General F-35 Forum

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