Forum: F-16 Procedures

First of all, I would like to thank the webmasters for the great site they have created. Does anybody know what the function is of the trim settings ansd the drift correction switch?

What is the function of the trim settings? I can imagine that they are useful when the jet has an asymmetric configuration. But, according to the F-16 C/D block 52 checklist, a pilot has to set the trim settings to normal after engine start and to take off settings before take off, where there is no question of such a configuration. Furthermore, nowhere the checkilst says that those settings have to be reset after take-off. Why are they needed on take off and not resetted later in the flig?

Secondly, thete is a drift correction on the ICP. What's the function of it? Doest it allow the pilot to override any computation the FCC makes when releasing bombs? Why is this switch set to normal before taxi and set to drift when the jet is airborne? When the pilot is due to land, he resets it to normal

I've checked the Falcon 4 manual, but it provides no answer.

greetings

Jeroen

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The drift / normal switch effects the flight path and pitch ladders in the HUD (the SuperPak 3/4 manual covers it Very Happy

). Basically in normal its fixed to the centre of the hud, in drift it is allowed to offset itself depending on the prevaling winds. From what i've seen so far it could be very handy for landing in a crosswind as it seems to show you where the aircraft is actually flying not just where the hud is pointing.

As for trim, when I fly (and many others) regular GA aircraft one ususally trims for a certain climb upon takeoff...i'm not sure that you would do this in a fast jet though....in fact in flight the trim wheel gets a good workout for all sorts of climbs and descents.

Last edited by LinkF16SimDude on Aug 30, 2004 - 03:54 PM; edited 1 time in total

kneecaps wrote:

Basically in normal its fixed to the centre of the hud, in drift it is allowed to offset itself depending on the prevaling winds.

Wellllll...not too pick to many nits but the amount of displayed drift is really the computed Velocity Vector taking into account other factors besides just prevailing winds (pitch/roll/yaw rates, airspeed, etc.)

For the pre-block 40 jets the trim needs to be centered during ground ops for the FLCS self test. If the trim is too far off center during the test, the test will fail. Not sure about digital FLCS systems though, and hopefully a block 40/50 guy will speak up.

Personally, I use the roll trim quite a bit as depending on the config, the jet tends to roll to one side if it's heavier due to an assymmetric stores load. I also will use the yaw trim to center the "ball" at the bottom of the ADI to get any slip out of the jet once airborne. Our jets have been flown pretty hard, and are a bit bent requiring some yaw trim.

The HUD symbology will shift depending on the crosswind. The more crosswind, the more the symbology is pushed to the side. If there is enough crosswind, the flight path marker will have an X over it indicating it is not a valid indication of where the flight path is. The Drift C/O switch will center the symbology, which will allow me to see the symbology better, but the FPM will only be accurate in pitch not azimuth since I took that out w/ the switch.

Gus,

Quote:

Our jets have been flown pretty hard, and are a bit bent requiring some yaw trim.

I bet that would cause som interesting allignement issues when replacing some of the bigger parts like the engine etc.

Naw... The jet does pretty good.

Cylon

By bent, I don't necessarily mean physically bent. Over time, the flight control surfaces of the jet tend to move out of the original rigging positions when the jet was built. As a result, the jet doesn't fly quite right requiring some trim inputs.

If the jet was bent so much the engine install would have problems, I don't think it would be airworthy.

Block 40 and 50 they are samelike 25 and 30. Only difference you dont run bunch of unnecessary bit steps. Alternate flap switch norm. Trims neut. (otherwise it fails. Run bit once it finishes bit till end. (It is good if you little warm up before).

Twisted Evil

Gus wrote:

For the pre-block 40 jets the trim needs to be centered during ground ops for the FLCS self test. If the trim is too far off center during the test, the test will fail. Not sure about digital FLCS systems though, and hopefully a block 40/50 guy will speak up.

Yes, on DFLCS the trim needs to be centered for FLCS BIT to pass. Believe or not, but the AoA probes also need to be centered, or at least symmetrical to pass or it will cause a FLCS 055.

Forum: F-16 Procedures

Trim settings and Drift Co switch