A while ago I saw a post indicating that spoilers were not always deployed on touchdown even if armed; and I've noted the same thing myself. I've figured this behavior out, tho, and how to get them to work 100% of the time.If you set the speed brakes up ("/") on descent for drag to maintain a path descent, you must put them fully down ("/" again) before arming for touchdown ("shf-/"). Verify this by looking at the throttle panel.If you put them up for drag and then arm them directly from the up position without first putting them down, the lever appears in the armed position and the "speed brake armed" indicator indicates that they are armed, but when you touch down the lever will move to the down position and the speed brakes will not deploy.I've probably been flying this way too much...Regards -- Dick Bixler

"If you put them up for drag and then arm them directly from the up position without first putting them down, the lever appears in the armed position and the "speed brake armed" indicator indicates that they are armed, but when you touch down the lever will move to the down position and the speed brakes will not deploy."Unfortunately, it didn't make any difference in my case :-( Even if I don't use the spoilers in flight, it still refuses to work.Can you think of anything else you did which may have fixed it? (Ever hopeful!)Thanks.Cheers.Ian.

P.S. After a few more touch and goes and lots of reading of manuals, I thought I'd figured out what the problem was. As I am flying PMDG at relatively low weights, my dodgy Radio Altimeter readout, on the ground, is sometimes 10' or more. According to the Boeing Maintenance Manual, the Auto Speedbrake will not work if the Radio Altitude is not less than 10' (It is the final safety interlock). My last landing, however, was somewhat firm, and the RA indicated a permanent 8'. It still didn't activate the Speedbrake actuator (d@rn!).I was also wondering if the 737NG autospeedbrake would work if you ARMed it on the ground: On aircraft like the 747-400, if you put the Speedbrake Lever to ARM on the ground (with the throttles at idle), it immediately drives aft, automatically. However, looking at the wiring schematics for the NG, it looks like the logic for activating the Speedbrake actuator needs to see either wheel spin-up (to 60kts), or an AIR to GROUND transition. In the latter case, the speedbrake actuator appears to have a time limit (the actuator only drives for 4 seconds, but, as all pilots are aware, in most cases speedbrake levers are so quick they will take your arm off in you're not careful!).Idea for test: Place the speedbrake lever in ARM (on the ground), accelerate to almost 60kts groundspeed and then slam the throttles back to idle.... If your forward momentum carries you above 60kts, the logic for speedbrake actuation should be triggered. Any volunteers? :-)

Ian your correct on the 60kts spin up, to test the autospeed brakes on the ground you can simulate the 60kts on the autobrake controller in the EE bay, unlike other Boeings where the speedbrake will deploy and stow with reverser and throttles.And speaking of RA it should indicate -4 on ther ground as opposed to the -11 it reads on the PMDG bird.

Ian - My approach is 2-channel a/p app, a/t on and speed set to vref indicated in FMC, f/d on, gear down at final clearance, flaps per FMC approach ref. Switch off a/p channels on touchdown and push down the nose. Reversers and wheel brakes. Sound right? This works every time for me. Dick Bixler

"And speaking of RA it should indicate -4 on ther ground as opposed to the -11 it reads on the PMDG bird."I think you made the same mistake I did, Wallace. You assumed it was minus... It's actually plus 11 feet ;-) It's probably because we're used to seeing minus values in the real world.Thanks for the tip on the Autobrake Controller... reading about it now in the BMM. I may have a few more questions coming up shortly ;-)Cheers.Ian.

Thanks, Richard... I'll give it a try.As far as I know, however, the Autospeedbrake should run independently of the A/P... up to a point. Can someone confirm this is the case in PMDG?In real life, the Radio Altimeters send height signals to the A/P computers and the A/P computers energise external "less than 10feet" relays when the aircraft descends below 10'. This allows the speedbrakes to deploy (when other prerequisites have been satisfied). This process should happen with or without the A/P's engaged, but not if you start pulling A/P system circuit breakers ;-)My Autobrakes seem to be working normally, so a lot of the logic which activates the AutoSpeedbrakes seems to be satisfied. Speedbrake Lever and Radio Altitude signals are the only things different. If we eliminate RA signals as the cause of my problems, then that only leaves the Speedbrake Lever position logic (the SB Armed light is shining brightly, so I assume that part of this logic is working correctly).Cheers.Ian.

Forgot, throttle full back during approach since speed is controlled by MCP in this config, and throttle back is required for reversers. - just for a more complete description...One more thing, SB Armed light shining does NOT indicate that logic is set, as I described in my original post. This may not apply directly to your situation, but apparently the light and the logic may not always be in sync. Put up the throttle panel when you land, what happens to the speedbrake lever? I bet just after touchdown it stows the spoilers rather than deploys them. Another experiment... db