Landing with stores, fuel tanks, and CAT III configuration

[Al-Azraq]

Hello!

 

So I'm learning the Viper and thoroughly enjoying it, I think it is my favourite modern jet already.

 

Of course, one of the procedures I'm practicing more are landings and I manage quite well without stores and CAT I configuration. However, yesterday I did a full strike mission for the first time and as I wasn't attacked by any enemy jet so I came back with the 4 Aim-120s and the two bags (empty, I didn't drop it because I wasn't engaged in a dogfight and they are expensive).

 

When attempting landing I went for a pattern as always but I messed up because I was in CAT III configuration as I had the fuel tanks on me, but also the additional weight which I'm not used to.

 

So I have some questions about how to approach this situation: do I have to perform direct approaches under certain weight and loadout configurations? Is changing to CAT I required for landings regardless your loadout?

 

I have searched online but have found nothing, just that there is no maximum landing weight for the Viper.

 

Thanks in advance!

[Cepheus76]

I suggest to make the downwind leg a bit wider, i.e. fly a bit further away from the runway than normally. This way you have enough room to fly the base turn at the higher required approach speed and still use normal bank angles.

[Furiz]

Just adopt to the situation, fly that downwind leg a few times without landing, get the feel for it, eventually it will be just the same as if you were in CAT I

[Florence201]

Aim to break at with G at 1% of airspeed through the turn. 

[Ignition]

The F16 flies like a rock on base and final, its not like the F18 which is super easy. When I know I'm not going to do the base very well, I do the downwind a little bit further (1.5nm)  and/or extend the downwind a little. Also I check the wind direction so I don't drift to the airport while I fly the downwind.

 

[Steel Jaw]

1 hour ago, Ignition said:

The F16 flies like a rock on base and final, its not like the F18 which is super easy. When I know I'm not going to do the base very well, I do the downwind a little bit further (1.5nm)  and/or extend the downwind a little. Also I check the wind direction so I don't drift to the airport while I fly the downwind.

 

 

The carrier based nature of the Hornet can cover up a lot of landing sins to be sure...the Viper requires alot of finesse.

[Frederf]

You're not going to exceed 15 AOA in any landing process. Do not change CAT I/III switch for landing or in any situation which places the FLCS in a lighter category than your actual configuration. The base turn of the overhead procedure shouldn't be too different near MLGW but if anything it's a little wider of a pattern.

[Lace]

Doesn't the Viper automatically go to CAT/III when the wheels are down (or AAR door is open) anyway?

[Cepheus76]

1 hour ago, Lace said:

Doesn't the Viper automatically go to CAT/III when the wheels are down (or AAR door is open) anyway?

I am certain that the way the FLCS processes control stick inputs depend on gear and AAR door position. If I remember correctly, with gear down/ AAR door open, the pilot commands a certain pitch, but in normal cruise configuration stick position is interpreted as a demand for a certain g-load.

 

The stores config switch, as far as I know, controls the maximum g's which are available, regardless of aircraft configuration.

[Lace]

18 minutes ago, Cepheus76 said:

I am certain that the way the FLCS processes control stick inputs depend on gear and AAR door position. If I remember correctly, with gear down/ AAR door open, the pilot commands a certain pitch, but in normal cruise configuration stick position is interpreted as a demand for a certain g-load.

 

The stores config switch, as far as I know, controls the maximum g's which are available, regardless of aircraft configuration.

 

Yeah, I know there is some change, just couldn't quite remember what it was exactly.  Pretty sure CAT/III limits roll and pitch rates too, but happy to be corrected.

[Cepheus76]

1 hour ago, Lace said:

 

Yeah, I know there is some change, just couldn't quite remember what it was exactly.  Pretty sure CAT/III limits roll and pitch rates too, but happy to be corrected.

I just had a look into the documentation of that other sim. You're right, the position of the stores config switch also has an effect on the pitch and roll rates too. 

[Frederf]

5 hours ago, Cepheus76 said:

I am certain that the way the FLCS processes control stick inputs depend on gear and AAR door position. If I remember correctly, with gear down/ AAR door open, the pilot commands a certain pitch, but in normal cruise configuration stick position is interpreted as a demand for a certain g-load.

 

The stores config switch, as far as I know, controls the maximum g's which are available, regardless of aircraft configuration.

Certain changes affect the FLCS. There are different FLCS gains: cruise gains, landing gains, standby gains. The CAT I/III switch is a separate concept. So you can be in cruise category I, cruise category III, landing category I, landing category III, and I have no idea if standby gains is any different related to category switch. Standby is failure mode. Each gains is also split into a low and high speed laws.

 

Putting down the landing gear (handle) or opening the AAR door puts you in landing gains but it doesn't put you in CAT III. The only thing that puts you in CAT I or III is by flipping the cockpit switch. Famously pilots will sometimes AAR with a category I config with the switch in CAT III to make refueling easier. But in both cases they are in takeoff and landing gains. If they approach the tanker with the AAR door open at <400 knots they'll see a FLCS change as they decelerate <400 knots.

 

The CAT I/III switch changes FLCS laws and values. Technically the maximum command G does lower in CAT III but primarily the limiting value is AOA. The purpose of CAT I/III is to prevent the airplane from departing controlled flight. It does not protect against over-Ging the airframe or the stores or the pilot. Pitch, rudder, and roll laws are changed with the stores config switch in III which makes a more docile feeling airplane in general.

 

You never put the switch CAT I unless the airplane is category one configuration. You're allowed CAT III in either configuration for comfort or response reasons. I've never seen the need in the landing pattern to soften the airplane. It already flies quite calmly. Once the gear is down and in landing gains everything should be cake.

 

Here's my attempt at a ~102% MGW overhead and landing. I used normal config cat III, 300 knots initial. No way can I hit the 1% of G target. I get to the AOA limit before then so I just follow 13AOA donut in the break turn. Lateral spacing is about 150% normal. Gear down midfield and at perch something like 220 knots is on speed AOA. I essentially ride MIL in the base turn. I think my key position was a little late so I have a small level segment at the end. Based on fuel readout touchdown was about 101% MGW. Minimum run landing technique I had about 1000' left to go.

 

I did it again in CAT I and didn't notice anything different or certainly nothing that helped me plus it's illegal. Technique was a bit better though as base turn didn't end up low. For variation I put the speed brake out before break turn like you'd normally do at a normal weight overhead and it was also fine.

 

This is an extreme case of overhead at 100% (or more) MGLW and it still can be done. With a less ridiculous load (30, 36klb) it is closer to a normal overhead. It's no fun and things have to be slightly modified but it's still safe and effective.

F16 MGW Overhead.trk F16 MGW Overhead 2.trk

[LJQCN101]

Myth buster time.

 

Actually the CAT I/III switch doesn't matter in Take-off & Landing Gains. (Calling landing gains for less typing below.)

 

For the Longitudinal DFLCS, the CAT III AOA limiter schedule is multiplied by zero (nulled) under Landing Gains. And there's yet to see any extra filtering of command signals or feedback signals due to CAT III.

 

For the Lateral DFLCS, the roll rate limiter output is fixed at 167 deg/s under Landing Gains, overriding any dynamic roll rate limiting schedule of CAT I/III and Cruise Gains.

Edited September 4, 2021 by LJQCN101

[Frederf]

Huh, I have heard about AAR in cat III having an effect. Is that an older version of FLCS or just a myth?

[Cupra]

Myth... CAT switch does not effect the FLCS in different configurations. Wir AAR door open it changes, gear down changes...

 

And more loadout does just change the landing speed... 154kts plus 4kts for each 1000lbs of fuel and stores... You can land with a full loaded jet.. no problem, if it takes off it can land. No need to drop anything, just train more  

[Dee-Jay]

12 hours ago, Cupra said:

Wir AAR door open it changes, gear down changes...

 

More precisely, landing gear handle ... and/or Manual Flap extend.

[LJQCN101]

16 hours ago, Frederf said:

Huh, I have heard about AAR in cat III having an effect. Is that an older version of FLCS or just a myth?

Cross checked with -1, it also states that in takeoff and landing gains, the STORES CONFIG switch has no effect on limiting or gains. 

[Al-Azraq]

On 9/4/2021 at 5:28 PM, Frederf said:

Certain changes affect the FLCS. There are different FLCS gains: cruise gains, landing gains, standby gains. The CAT I/III switch is a separate concept. So you can be in cruise category I, cruise category III, landing category I, landing category III, and I have no idea if standby gains is any different related to category switch. Standby is failure mode. Each gains is also split into a low and high speed laws.

 

Putting down the landing gear (handle) or opening the AAR door puts you in landing gains but it doesn't put you in CAT III. The only thing that puts you in CAT I or III is by flipping the cockpit switch. Famously pilots will sometimes AAR with a category I config with the switch in CAT III to make refueling easier. But in both cases they are in takeoff and landing gains. If they approach the tanker with the AAR door open at <400 knots they'll see a FLCS change as they decelerate <400 knots.

 

The CAT I/III switch changes FLCS laws and values. Technically the maximum command G does lower in CAT III but primarily the limiting value is AOA. The purpose of CAT I/III is to prevent the airplane from departing controlled flight. It does not protect against over-Ging the airframe or the stores or the pilot. Pitch, rudder, and roll laws are changed with the stores config switch in III which makes a more docile feeling airplane in general.

 

You never put the switch CAT I unless the airplane is category one configuration. You're allowed CAT III in either configuration for comfort or response reasons. I've never seen the need in the landing pattern to soften the airplane. It already flies quite calmly. Once the gear is down and in landing gains everything should be cake.

 

Here's my attempt at a ~102% MGW overhead and landing. I used normal config cat III, 300 knots initial. No way can I hit the 1% of G target. I get to the AOA limit before then so I just follow 13AOA donut in the break turn. Lateral spacing is about 150% normal. Gear down midfield and at perch something like 220 knots is on speed AOA. I essentially ride MIL in the base turn. I think my key position was a little late so I have a small level segment at the end. Based on fuel readout touchdown was about 101% MGW. Minimum run landing technique I had about 1000' left to go.

 

I did it again in CAT I and didn't notice anything different or certainly nothing that helped me plus it's illegal. Technique was a bit better though as base turn didn't end up low. For variation I put the speed brake out before break turn like you'd normally do at a normal weight overhead and it was also fine.

 

This is an extreme case of overhead at 100% (or more) MGLW and it still can be done. With a less ridiculous load (30, 36klb) it is closer to a normal overhead. It's no fun and things have to be slightly modified but it's still safe and effective.

F16 MGW Overhead.trk 2.16 MB · 3 downloads F16 MGW Overhead 2.trk 1.99 MB · 2 downloads

 

Thanks for your detailed post and taking the time to test. I will check those Track files as soon as I get home!