Dot Speed command

[Zener]

Last night trying to climb out in a bomber my .speed command was totally disfunctional. I used it earlier in the day, in fact on that same flight earlier (it worked) but after a manual climb period it would not respond.  Is there something I'm doing wrong or does auto pilot climb mode effect this in some way?   

[TequilaChaser]

When you say "Auto Pilot climb mode" are you referring to Shift X or Alt X?

[Zener]

I'm referring to the auto pilot mode that lets you hold a fixed climb, guess it's shift-x but i can't remember as I have it mapped to a controller button.

What happened is i left the base on default climb in B17s.  Then we ( was flying with other bombers) set the dot speed for a 125mph climbout.  Worked fine.  As some bombers didn't set for that they pulled ahead, so I manually set my climb by nosing down a tad and setting it on auto pilot climb.  When caught up, we all went to .speed 125 again except I got no response from it.  The dot speed would not work.  I even went level auto pilot (X) and tried from there - no joy.  Auto pilots off - still nothing.

So I'm wondering if I'm doing something wrong that's disabling that command and if so what I need to do to get it back on?

[FLS]

Shift X holds your current pitch attitude. Alt X is auto speed/climb.

[1ijac]

Hit alt+X first, then your .speed. 

[ImADot]

Hit alt+X first, then your .speed.

You can do either one first. You should be able to set your desired speed at any time, whether you've engaged the autopilot or not.

[Zener]

Well I will give the alt-x thing a try if it happens again and will report results.  You know how it goes when you WANT to replicate something odd.  Thanks for the replies.

[pembquist]

I don't fully understand your description but since you have been using .speed you probably already know this:

.speed sets the IAS for the autopilot mode that holds your heading, it does not adjust your throttle but merely holds a pitch attitude that with your throttle setting will give a constant IAS set by .speed. The default Keys are alt X.

The other two autopilot modes are unaffected by .speed and fly a fixed pitch regardless of speed, they will stall your airplane if you have insufficient power to maintain flying airspeed at the pitch selected.

On takeoff the airplane is in Take Off mode which transitions to speed mode at some point. 

I have found that sometimes after doing an auto takeoff and climb out I will type .speed with the plane still in autopilot to set a higher speed, the plane will nose over and rather than diving I will either put it in level autopilot or manually fly until it is going at the speed I set with .speed. Then when I reengage alt X it is as though I never typed a new .speed value and the plane pitches up to the default speed setting. If this happens I disengage the autopilot type in speed again while disengaged, reengage alt X and it works.

[colmbo]

Just for giggles, 135 IAS will yield a better rate of climb and be a bit easier to hold formation since you won't be as close to stall.

[TequilaChaser]

Good morning Zener,

Just wanted to check in on this thread and follow up, to see if everything is working correctly for you now...

I figured that you may have been using the wrong auto mode for what you was trying to accomplish. So I asked my original ? thinking that it would give you a hint and an "oh yeah, I know what I need to do"

So just checking to see if everything is working correctly for you now....

Good recommendation, colmbo!

Great detailed description and information, Pembquist

TC

[Zener]

Well so far it's been working fine, I haven't had it not work in the three times I used it since posting.

On a mission two nights ago I kept changing the .speed and going in and out of ALT-X auto pilot mode to see if I could get it to reproduce the symptoms I had a week ago.  Nothing, the dang thing worked perfectly like it always had.

I can stay in ALT-X mode and the .speed commands will change speed - which is my understanding of how it is supposed to work.  Now if I am NOT in that mode, the only time .speed alone has any effect is if I'm already in the default climb you end up in with auto takeoff engaged.  I presume that is because you ARE in that mode, you just didn't have to type ALTT-X to get there.

If I type .speed xxx when not in that mode of autopilot, I won't see anything until I use that mode, and then it will seek the speed I typed (same flight).

So that's how it's working now, but didn't a week ago.  I have no clue why it did that, use same commands, my controller didn't catch fire or anything, so I guess I chalk it up to just one of those weird things.  I'd hate to think my controller is imposing it's own version of ENY with autopilot modes. 

Thanks for all the good info in the replies to this thread, and thanks for checking back with me.