Any idea why reverse thrust simply does not work sometimes?

[DmitriKozlowsky]

Any idea why reverse thrust simply does not work sometimes? On landing,

Landing with 180 knots IAS. At touch down activate thrust reverser (handle pulled, light is on), go to full power, gear brakes at 50 %, but aircraft does not slow down. Most other times,it works fine. Does afterburner deactivates reverser?

[LazyBoot]

15 minutes ago, DmitriKozlowsky said:

Any idea why reverse thrust simply does not work sometimes? On landing,

Landing with 180 knots IAS. At touch down activate thrust reverser (handle pulled, light is on), go to full power, gear brakes at 50 %, but aircraft does not slow down. Most other times,it works fine. Does afterburner deactivates reverser?

Front wheel on the ground?

[DmitriKozlowsky]

OK thank you. So must have three point contact with runway.

[LazyBoot]

2 hours ago, DmitriKozlowsky said:

OK thank you. So must have three point contact with runway.

Yes.

It's also worth noting that if you pull the reverser handle while still in the air (or nosewheel off the ground), it'll arm the reverser to activate when you do get all wheels on the ground.

[DmitriKozlowsky]

Got it. That's too bad actually. A thrust reverser that is activatable in forward flight, is vectored thrust, and would allow aircraft to slow down fast. I get it is a risk of erroneous or uncommanded reversal. In civilian aircraft that is an unacceptable risk. But in a combat aircraft, it may be.

[renhanxue]

The Viggen has absolutely no problems with slowing down fast if it needs to, just turn and you'll get rid of speed in a hurry. Also the thrust reverser really messes up the yaw stability, it'd be very dangerous to use in the air and there are multiple safety interlocks that prevent it from happening.

Edited February 25, 2022 by renhanxue

[DmitriKozlowsky]

OK good to know.

[DmitriKozlowsky]

On 2/25/2022 at 2:12 PM, renhanxue said:

The Viggen has absolutely no problems with slowing down fast if it needs to, just turn and you'll get rid of speed in a hurry. Also the thrust reverser really messes up the yaw stability, it'd be very dangerous to use in the air and there are multiple safety interlocks that prevent it from happening.

 

I do notice that it bleeds energy in hard turn or max perf break, awfully fast. But overall I really like the flight model and flying qualities of Viggen. When it only carries two AIM-9P or L, and nothing else, internal fuel at 70% or less , its quite a peppy. But weighed down with weight and drag of gunpod and jammer, it looses some peppiness. I am not clear why Swedes decided to design a fighter-bomber without internal organic cannon , ECM, and countermeasures dispenser.  Why everything has to be a pod taking up a station. Since 2.7.10XXX added low altitude buffet flight dynamics, Viggen behaves quite nicely compared to F-16 and Harrier. Buffeting is most apparent over Cyprus, flying down among the mountains of Western Cypress, in Viper or Harrier, there is considerable yaw and pitch oscillations. Present in Viggen, but not as much. Probably because it is heavier ship and canards help. I recall that B-1B gained cunnards during development to reduce low altitude buffet. Low altitude buffet was a factor in more then few F-111 CFIT losses and airframe maintenance woes.

[renhanxue]

The AJ 37 is a strike aircraft with only very limited A2A capability. The fighter variant is the JA 37, and that one does have a cannon and integrated countermeasures dispensers.