Forum: F-16 Design & Construction

Hi,
I was thinking that wouldn't it have been more suitable if the throttle was just fixed at its place and in order to throttle up or throttle down, there would have been a roller at the top, just like an optical mouse ?
It would make HOTAS mechanism even more effective. Is there any drawback in the throttle system I have suggested ? Because to me, it would have been much more easier. Then why wasn't this design adopted ?
Just a general knowledge question.
Thanks anyways.

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The primary means of 'communication' between the cockpit and engine is mechanical; unlike the rest of the aircraft that is electronic communications. The GE F110 uses an 'electronic backup' signal if the cable was to fail, but PW F100s strictly use the mechanical input as the sole source for PLA (Power Lever Angle) The Viper's throttle is more like the push/pull knob of s Cessna, but attached to a 'stick' that has all the other HOTAS controls attached.

There is a cable that runs from the throttle quadrant in the cockpit to engine bay. As the throttle is advanced by the pilot, the cable moves forward/aft. The rear of the cable is attached to a rack in the engine bay. The rack takes the cable's push/pull movement and makes it rotational (Clockwise, Counter-Clockwise). This rack is attached to the engine by a throttle shaft, with universal joints for some flexibility, that is attached to the engine's PLA input. The PLA input on the F100's Main Fuel Control (MFC) or F110's Main Engine Control (MEC) then use the PLA for engine operation.

The MFC of the F100 takes the 'mechanical' PLA signal and 'senses' it into an 'electronic' signal at this point by use of a resolver, feeding the PLA to the DEEC (Digital Electronic Engine Control) or as most know it a FADEC. In the event that the DEEC fails, or some other condition exists where the engine can not operate in 'primary' mode, the mechanical input of the PLA always moves internal linkages/cams/valves to compute fuel flow in a hydro-mechanical mode; called 'SEC' or "Secondary Engine Control" mode.

There have been early Viper cases of aircraft loss if the throttle becomes disconnected at the engine. There are now multiple safe-guards, and inspections when attaching the throttle shaft to the engine. There has also been cases of 'stuck' throttle cables in the last few years that has resulted in at least one crash.

Your idea for a 'roller' would only work on newer generations of engines that use a purely 'digital or electronic' PLA source; but the throttle lever has proven to be very successful after the integration of all the HOTAS buttons/dials onto the grip.

Keep 'em flyin' Thumb

TEG

Thanks for the info brother. Very detailed info, as usual Very Happy

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But what I meant is that, the throttle should have been fixed with all the buttons/dials on the throttle grip with the workable IDLE Detent as well just like in today's F-16's, but in order to accelerate/retard, instead of pushing/pulling the whole throttle back, why not roll a roller ? I get it that it wouldn't work on the conventional F-16's, but wouldn't it suit the Block 50/52/60 versions ?? And I know that the newer versions of F-16's are almost never gonna engage in close-range dogfights but one could never tell what would happen when you get in there.
Thanks again for the info brother.

yasirbhojani wrote:

instead of pushing/pulling the whole throttle back, why not roll a roller ?

Like I said, would work with new generation all FADEC engines like the F135 that don't use mechanical PLA inputs. They rely solely on electronic PLA commands. One FADEC is the backup for the other FADEC. (Like the F119 the F135 has 2 FADECs that work together!)

yasirbhojani wrote:

I get it that it wouldn't work on the conventional F-16's, but wouldn't it suit the Block 50/52/60 versions ??

The F100 and/or the F110 would need to be completely redesigned, at least from the engine control system standpoint. With both motor's controls having a major component that is hydro-mechanical, a pure electronic signal won't work. I suppose you could use some sort of electro-servo motor to drive the PLA shaft on the engine's control. (Some test-cells use an 'electrical throttle' connection like this)

The only issue with any throttle arrangement is loss of input to the engine. In the mechanical throttle case, it is a broken/binding cable, mechanical failure of the mechanism, or becoming disconnected from the engine. In the electronic case, you have loss of signal, or loss of power.

I highly doubt anyone at PW or GE will be keen on 'modernizing' the F100 or F110's engine control system to eliminate the mechanical input. There just aren't enough remaining Viper sales to justify the investment. After all, GE had the best case with the F110, but for the sake of commonality with older Vipers, I don't think it was even proposed. It would negate the possibility of upgrading GE-100 or GE-129 Vipers with newer GE-132.

Keep 'em flyin' Thumb

TEG

Thanks a lot buddy. Great info. Got everything I needed to know...

There's a whole host of reasons I can think of, not the least of which is "if it ain't broke, don't fix it". How about a motorcycle type throttle? how about a gas pedal since the F-16 doesn't really need rudder inputs? How about voice activated?
How would the avg. pilot do finessing a scroll wheel under combat or at 9g?
What if his left hand becomes incapacitated and he needs to reach over and control the throttle with his right?
Also, it makes the hotas situation worse not better. The throttle is studded with buttons and wheels that the pilot needs all his fingers to use, the throttle itself is easier to manipulate if it is gripped and moved without having to use the fingers which are busy doing other things.

Quote:

How would the avg. pilot do finessing a scroll wheel under combat or at 9g?

You are so wrong. If it would have been possible, it would have been much more easier to scroll the roller than pushing or pulling the whole throttle grip.

Quote:

the throttle itself is easier to manipulate if it is gripped and moved without having to use the fingers which are busy doing other things.

Yeah, thats true. Thanks a lot.

yasirbhojani wrote:

Thanks for the info brother. Very detailed info, as usual Very Happy

.
But what I meant is that, the throttle should have been fixed with all the buttons/dials on the throttle grip with the workable IDLE Detent as well just like in today's F-16's, but in order to accelerate/retard, instead of pushing/pulling the whole throttle back, why not roll a roller ? I get it that it wouldn't work on the conventional F-16's, but wouldn't it suit the Block 50/52/60 versions ?? And I know that the newer versions of F-16's are almost never gonna engage in close-range dogfights but one could never tell what would happen when you get in there.
Thanks again for the info brother.

Hi yasirbhojani

One of the problems I think likely to be found in your idea is lack of feedback to the pilot.

As vegadave901 mentioned, the device would probably lack the finesse of a standard throttle, unless it was pretty big.

Already did that on a test setup. No problem with the mechanical cable motion took care of that with an actuator. Problem was, pilots that evaluated it didn't like the thumb movement as a good gauge of throttle position when looking outside cockpit as if in combat.

yasirbhojani wrote:

Thanks a lot buddy. Great info. Got everything I needed to know...

I wouldn't underestimate the capability to convert a F110 to full electronic capability.

F16JOAT wrote:

yasirbhojani wrote:

Thanks a lot buddy. Great info. Got everything I needed to know...

I wouldn't underestimate the capability to convert a F110 to full electronic capability.

There are many aircraft with fly by wire throttle arrangements but for some reason mechanical sticks or levers are still used? Most auto pilots actually have to use a servo to move the sticks or levers to "match" what the engine is doing.

As a side note the the latest version of GE's use a digital PLA signal as the primary signal, so the engine really is fly by wire. The mechanical cable is actually third on the list in the hierarchy of importance.

http://www.f-16.net/news_article691.html
The Block 60 aircraft and engine also will feature an auto-throttle capability.

The F101-DFE was also capable of F-B-W but Engine SPO backed out on letting full auto-throttle authority to be used on the F-16 earlier models due to "Immaturity" back in the early 80's due to experience with a single engine high performance fighter

Forum: F-16 Design & Construction

F-16 Rolling Throttle Design