Forum: General F-35 Forum

How exactly would you put two engines on the F-35 without re-designing it from the ground up?
Wouldn't you be better off just increasing the size of the single engine?

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count_to_10 wrote:

How exactly would you put two engines on the F-35 without re-designing it from the ground up?
Wouldn't you be better off just increasing the size of the single engine?

Two words: Reliability, Survivability.

@Southernphantom...... Do you have any data that says twin engine fighters are more reliable or survivable then single engine fighters? In fact "U.S. government Maintenance Reporting System statistics show that the F-16 (single engine) has a slightly better safety record than the F/A-18 (twin engine). "

Last edited by spazsinbad on Jul 14, 2012 - 01:27 AM; edited 1 time in total

Recent - thankfully - good story about 'double engine failure':

Navy: Jet crash caused by dual-engine failure By Kate Wiltrout, The Virginian-Pilot July 2, 2012

http://www.hrana.org/news.asp#NavyJetCrash

“The Navy said today that an F/A-18 Hornet that crashed into a residential neighborhood shortly after takeoff on April 6 experienced dual catastrophic engine failure – an extremely rare occurrence in high-performance combat aircraft. The Hornet relies on twin General Electric F404 engines to reach supersonic speeds. According to pilots who've flown the jet, single engine failures are rare, and dual engine failure is almost unprecedented.

The investigation found that the doomed jet suffered two unrelated & almost simultaneous engine malfunctions. The right engine failed first. When the pilot increased the throttle on the left engine to compensate, it failed to respond. The jet began losing altitude, & the pilots ejected when the jet was about 100 feet above the ground, according to the investigation...."
_______________

And to be clear....

Lessons From The Hornet Crash (NORFOLK VIRGINIAN-PILOT 03 JUL 12) ... Adm. John C. Harvey

http://www.hrana.org/articles.asp#Lesso ... ornetCrash

"...[Adm. John C. Harvey] we have done our due diligence to find the how, why and what behind this crash and prevent something like it from happening again. Many dedicated professionals and aviation experts have devoted considerable time and effort to conduct a thorough investigation.

We have a high level of confidence that we know what happened. Although we were unable to identify a smoking gun, we did find a substantial body of evidence to support the findings.

The results show that the aircraft suffered two unrelated, nearly simultaneous, catastrophic engine malfunctions. The first malfunction occurred in the right engine during takeoff when the pilot received warnings in the cockpit that the engine had stalled.

The pilot followed established procedures by taking both engines out of afterburner and then placing the right engine in an "idle" position. The pilot attempted to compensate for the loss of thrust in the right engine by increasing throttle in the left engine, but the left engine failed to respond.

At this point, the aircraft was severely underpowered and began losing altitude. At approximately 100 feet altitude, the aircraft began to roll to the right, and the air crew was forced to eject.

The investigation determined the pilots followed established procedures, and it cleared the air crew of any dereliction of duties or misconduct. Our experts also have concluded the outcome would have very likely been the same for even our most experienced crew...."

alloycowboy wrote:

@Southernphantom...... Do you have any data that says twin engine fighters are more reliable or survivable then single engine fighters? In fact "U.S. government Maintenance Reporting System statistics show that the F-16 (single engine) has a slightly better safety record than the F/A-18 (twin engine). "

Truedat...except on the ship. Problem is there is no data for single engine aboard ship since A-7/A-4. Lotsa problems with that -- different airframe, different generation technology etc etc. AV-8 and Pegasus don't count either since the current Mk (RR-408) is 'essentially' the same thing they IOC'd with back in the 70s albeit with new LPC fan, a FADEC, new turbine technology, and new IGV controller.

Yeah, that is certainly not comparing apples to apples. It is very safe to assume that had the US F/A-18s operated off the same surfaces the US F-16s did, the 18s would have a better record. The catastrophic loss rate of F-16s is higher than that of F-15s. F-15: 2.42 % to F-16: 3.82%.

The arguments about reliability are all well and good, but it still doesn't answer how you can "modify" the F-35 to give it two engines without completely re-designing it.

count_to_10 wrote:

The arguments about reliability are all well and good, but it still doesn't answer how you can "modify" the F-35 to give it two engines without completely re-designing it.

Hell, that's not so hard. Geogen once advocated building an F-35 with THREE engines.

count_to_10 wrote:

The arguments about reliability are all well and good, but it still doesn't answer how you can "modify" the F-35 to give it two engines without completely re-designing it.

You're correct. It's possible that F/A-XX would actually be said twin-engine/two-crew F-35, with quite a while set aside for modification. In any event, this would not be a simple process, but it would be better than trying to keep it under the direct umbrella of the JSF program.

redbird87 wrote:

Yeah, that is certainly not comparing apples to apples. It is very safe to assume that had the US F/A-18s operated off the same surfaces the US F-16s did, the 18s would have a better record. The catastrophic loss rate of F-16s is higher than that of F-15s. F-15: 2.42 % to F-16: 3.82%.

That's a really misleading statistic. Its not really accurate either when you compare the PW -229 on Block 50s and -15Es, which is a relative of the F135. There there have been no Category A incidents related to the F-16C/D Block 50's engines with approximately 300,000 flight hours, and four with the F-15E over 900,000.

Moreover the F-16's loss rates include data from its first decade of service when the fighter was known as the lawn dart due to its poor avionics and unreliable systems. The AF has since worked extremely hard to bring that level down, so that now the F-16 is considered one of the safer aircraft in the service.

Yeah, I agree with you, but it is still a more valid comparison than comparing loss rate of an F-16 to a plane that operates off carriers, as that is certainly more stressful (to both man and machine) and thus, more dangerous work.

1st503rdsgt wrote:

Hell, that's not so hard. Geogen once advocated building an F-35 with THREE engines.

I'd like to see a drawing of that!

HaveVoid wrote:

sewerrat wrote:

count_to_10 wrote:

Quote:

IMHO he will continue the F-35 program "as is", but will refocus future developments into the "Payload" concept. Two Cents

That was my impression as well.

IDK, but from reading things here and there, I get the impression that USN isn't sold on the idea of the JSF or stealth in general except in building a new breed of faceted boats and investing in UCAVs. I get the impression that if they could re-engine the superbug they'd be content until 2030 with their flying decoys (superbugs), which ain't bad for the USAF since they'd draw fire away from our boys in blue and nomex.
When was the last time the Navy lost a F/A-18 in combat? 1991? I wonder if that has anything to do with that mentality.

I'll speak for myself, but I can't be the only one who finds the notion that the USN acting as "flying decoys" for the USAF to be not only beyond rediculous, but borderline insulting? Tell me, what of the fleets of F-15Es's, A-10s, Golden Eagles, and upgraded F-16s that will remain in the fleet for some years yet, are they decoys too? How about the E-3s, RC and KC-135s, C-17s, and U-2s-simply decoys?

The truth of the matter is that Stealth is only of so much utility for the Navy. Your stealth is somewhat hampered by the fact that your mobile airfield has the RCS of a small nation-state. They have stated that they remain committed to the F-35C to phse out the legacy Hornets. While the Super Hornet may not be 5th Generation, I think you are significantly underestimating the most capable 4th generation Aircraft in the US' arsenal.

HV

Compared to the -35, and -22, all of those platforms are flying bullseyes. The USAF recognized that 25+ years ago. The USN doesn't seem to have that same commitment to LO aircraft. One on hand you read that the Navy is committed to stealth, and then you can find just as many resouces where they don't feel the need to go to an all stealth fighter fleet. They're comitted, and wrongly so the Superhornet as the backbone of the fleet through at least 2025. What's left of the USAFs legacy fleet will be a backup to the -35. Hell even the USAF announced its cutting the A-10 fleet down to size "early" to make way for the -35.

The Suphornet is fine jack of all trades, but nonetheless it's not the best fighter even compared to other 4th gen aircraft like the F-15E and F-16C. Its not as good in mud moving as the Strike Eagle. Its GE engines also don't perform well at altitude. If they wanted a re-engineered 4th gen fighter, seems they'd have been better served with a fixed wing re-engined variant of the Tomcat than the Superhornet. Most of the mainenence issues on the Tomcat were the massively complex hydraulic system and the vintage radar that dated back to the TFX program. It had outstanding bring back capability if it didn't drop its 2k pound bombs. The airframe was very strong with all of its titanium and laser welding.

southernphantom wrote:

count_to_10 wrote:

How exactly would you put two engines on the F-35 without re-designing it from the ground up?
Wouldn't you be better off just increasing the size of the single engine?

Two words: Reliability, Survivability.

Only one word: Supercruise. The laws of physics don't change. A larger diameter turbine can't supercruise as well as two smaller diameter turbines with equivalent airflow. The single, larger diameter engine will, all else being equal, have more thrust and lower specific fuel consumption. But it will Mach stall sooner.

However, two engines means twice as many moving parts, and twice as many opportunities for mistakes and failures. Plus twice the maintenance and more fuel costs. And it offers less than twice the chance of saving the plane or pilot. Many things that can take out one engine, can take out two. Many a failing engine manages to, itself, take out the second engine. And many things that can take out an engine can take out other critical parts of the plane, or even outright kill the pilot anyway. Closely spaced engines have little more damage tolerance than one engine. Widely spaced engines have a less than benign one-engine failure mode. Two engines, basically, is a very costly way to provide far less than two times the reliability of one engine. For the same lifecycle cost, you could realistically design, manufacture, and maintain one engine with about the same safety factor as two lesser engines. It'll give you better range, and lower fuel costs too. It just won't supercruise as well.

Now, if pulse detonation engines become viable, you can have one supercruise engine with few moving parts, and multiple redundant thrust elements. An F-35 with a pulse detonation engine the size of the F-135 would be an amazing F/A-XX.

The F-35 was designed from the ground up with one engine, yes. But that doesn't mean it's locked into a single-engine propulsion system or flight control system. If you used a pod of matched engines then you could use techniques to streamline maintenance procedures. You really are more concerned with airframe downtime than the downtime for the pair of engines. The next concern is whether the said cost of this strategy outweighs the benefit. Over glacial water you might prefer the higher operating expense.

Forum: General F-35 Forum

Navy admiral hints at jettisoning F-35 fighter