[WORKING AS INTENDED] Mirage 2000 ILS & Autopilot fails at 500 feet AGL

[Milomindenbinder]

Have been practicing ILS - Autopilot approaches.

 

Works perfectly at most airfields. My technique is to intercept the ILS at 12 NMi and 3,600 feet AGL, couple the autopilot, control speed, break off at 50 feet on the radar altimeter, slight flare and land. Great system for night / bad weather recoveries.

 

At some airfields, the system goes breaks at about 500 feet AGL, the controls are sloppy and aircraft attitude changes without control input. First three landing were controlled crashes. Recovery is to apply full power, clean up and go around for a manual landing.

 

Tested airfields for repeatable failure are : Sochi-Adler RWY 06, Tblisi RWY 13, Mineral'nye Vody RWY 30. The loss of control seems to be consistently at about 500 feet AGL on the radar altimeter.

[Ramsay]

Autopilot Operational Limits

 

Max Alt 50,000 ft

Max Pitch +/- 40°

Max AoA 18°

Max Roll 60°

Min Speed 200 KIAS or 18° AoA if AP in ILS approach

Min Alt

• Normal Mode 500 ft

• Localizer & Glide slope mode 200 ft

• Altitude hold 1,000 ft

 

I haven't tested the autopilot localizer/glide slope mode in a long time but common reasons for AP disconnect were being below minimum speed and/or altitude.

 

With regards to hard landings, a common issue is being above the Max Landing Weight

 

With full A/A payload (2x 530s; 2x Magic IIs; 1x Fuselage ext. tank), you should land with 950kg of fuel to be at normal MLW. Or 3350kg to be at overrated MLW (which requires specific precautions to be taken, e.g. descent rate, parachute use...)

 

 

If you are still having autopilot issues, please post a short track demonstrating the problem.

 

Note: AFAIK the autopilot/ILS is designed to get the pilot to the decision height (200 ft AGL / 550m visual) and is not intended to be used like an autoland/cat 3 system.

Edited August 15, 2020 by Ramsay
Min Speed = 18° AoA if AP in ILS approach

[El Chapo]

IRL the autopilot will work just fine in altitude down to the ground!

The 200' or 500' minimum altitude is just a way for Dassault to say they do not garantee anything below.

By itself, the AP has no way to know it is below 500' (no RA needed to work).