Question regarding QFE

[Swiso]

Hello,

I love the Viggen, it is an amazing plane...one of the most exciting to fly and I am quite comfortable in flying it.

One thing that I have not yet understood is when you have to set the QFE...

 

Let suppose you create a flight plan....it contains 7 waypoints and waypoint 5 is the target.

 

I see in the knee board that each waypoint has his QFE value....

Do you guys set the correct QFE when going for that waypoint ?

Do you correct each time the QFE ? Or you set the target QFE after passing the IP ?

 

Can someone advise me on what the correct way to use it should be ?

Thanks

[randomTOTEN]

LS = QFE (0M)

B1-B4 = QNH

M5 = QFE (set as part of attack setup).

B6-B7 = QNH

L1 = QFE

 

That's how I'd do it. I also set QNH on the standby altimeter so I always have an MSL reference for the entire flight.

Edited June 8, 2020 by randomTOTEN

[Palten]

Correct QFE is very important for certain weapong to hit correctly, such as high drag bombs so what I usually do is check the QFE for the target and after takeoff simply set that QFE on the altimeter so I don't forget it later. Also the altimeter switch has to be in LD (LuftData/"AirData") and not in RHM (RadarHöjdMätare/Radar altitude).

But when flying (usually low) between B-points before the M-point, I use RHM.

[Swiso]

Correct QFE is very important for certain weapong to hit correctly, such as high drag bombs so what I usually do is check the QFE for the target and after takeoff simply set that QFE on the altimeter so I don't forget it later. Also the altimeter switch has to be in LD (LuftData/"AirData") and not in RHM (RadarHöjdMätare/Radar altitude).

But when flying (usually low) between B-points before the M-point, I use RHM.

 

Thank you, that's what I wanted to know.

When you say the altimeter has to be in LD mode, you mean in the flight plan part when you are not flying low level ?

Assuming your entire flight plan is low level flight (below 600m), one can set the altimeter to RHM, right ?

Thanks

[Palten]

No, you can fly with radar altitude but when performing bombing runs and such it's important to flip the switch over to "LD" so that the altitude is correct for the target area. You know where the switch is?

[Swiso]

No, you can fly with radar altitude but when performing bombing runs and such it's important to flip the switch over to "LD" so that the altitude is correct for the target area. You know where the switch is?

 

 

Ah...I see it...i believed that RADAR was more precise than LD.

Yes, I know where that switch it is:

[Palten]

Maybe, but radar altitude only works up to a certain level above ground, same in Hornet e g:thumbup:

[kengou]

No, you can fly with radar altitude but when performing bombing runs and such it's important to flip the switch over to "LD" so that the altitude is correct for the target area. You know where the switch is?

 

Source for this? I’ve been flying the Viggen tons and completed the campaigns for it, never had issues with weapons hitting on target, and I don’t think I’ve ever switched to LD. I leave it on RHM all the time.

[Palten]

Sources are retired Viggen pilots.

However, DCS is a simulation and not 100% as the real world so maybe most weapons will hit regardless of correct QFE. I will do some testing :)

 

edit: So, did some quick testing. Rocket attack, BK90, dive bombing and level bombing (both high and low drag test) Short version, level bombing will not work w/o correct QFE set. I tried using both RHM and LD and it seems that does not matter, BUT correct QFE for the target area has to be set.

Edited June 12, 2020 by Palten
More info

[TLTeo]

I was always under the impression that QFE mattering depends on the weapon delivery mode. For anything using radar ranging, it's unnecessary.

[alftand]

I was always under the impression that QFE mattering depends on the weapon delivery mode. For anything using radar ranging, it's unnecessary.

 

This is true. If QFE is not set correctly you can actually see the sight reticule jump as the impact solution shifts from triangulation to radar ranging. For this reason it is still good to set the correct QFE, or you might have to do a sharp correction when the radar ranging kicks in.