Riddle Me This Batman

[kent4142]

Hi All,

Again that was great fun meeting everyone in Chattanooga!  Thank You to the work horses that put it together and made it work.

But back to my post.  I took my 81 Dash 10 Commander 840 to Rockland Maine last year, and I just got back last night from another trip.  I have owned the airplane for two wonderful years so far, but I have a conundrum.  Only in Maine, when I come back to the aircraft after 1 or two days, I find the flaps down.  At first I thought I was forgetful and left the handle down - but no, both times the handle was up.

I have left the aircraft for more than 25 days without touching the aircraft and the flaps have never come down on their own.

I am putting my stupidity out there for all to see.  What is going on with the flaps?

Thanks.

Kent

[donv]

Mine does the same thing. Sometimes it can sit for weeks, flaps stay up, and sometimes they droop after a day or two. I have no idea why. Most of the time, they stay up.

[Badger]

You are setting the flap switch to neutral before leaving the cockpit, right?  When I see mine drooping, it is always because I forgot that step. 
ed

[kent4142]

Okay, you got me on that one.  I have never put the flap handle in neutral.  (except when I choose 1/2 flaps in flight.). I have always been returning the handle to the up position.

Standard procedure then should be:  Always leave the flap handle in the neutral position?

Kent

[schrambow]

Ok,
my 2 cents worth here,
For many years, i have always left the flap handle the neutral position as it does help very much to keep the flaps up after sitting for many days/weeks.  However, i was told by a very experienced Commander pilot that i should leave them in the up position when shutting down the plane, and told- who cares about drooping flaps anyway?. Well after hitting my head a few times on the buggers that last few years, i am back to putting them in the neutral position and my head doesn't hurt much anymore.
For 20 plus years operating the 680FLP i have never had an issue with leaving them in the neutral position but i do live close to the north pole it feels like at times throughout the year.
Now, i am not giving anyone advice here as everyone has a machine and probably a different opinion/experience here.
Maybe a mechanic that really knows the hydraulic system in and out can verify this here, but when leaving them in the neutral position you actually somewhat,"pressurize" the fluid within the valves.  When moving the flap handle into the up position, you don't "pressurize" the fluid between the valves and it will eventually dump the flaps over time- varies between each individual plane.
Not sure if there are any examples out there on this, but pressurizing the fluid (flap in the neutral position) and putting some heat on the hydraulic system (by sitting on a hot ramp in the sun all afternoon), could possibly cause the excess pressure and stress on the orings and seals, and maybe a hydraulic leak.
680FLP has main pressure of 3000 psi skydraul, 840 has 1000 psi of MIL-PRF-83282,  Not exactly sure of what pressure actually runs through the flap system though on each bird.
Anyway, sorry for the long post here, it would be interesting if someone could give their experience of any problem or issue in the past with leaving the flap handle in the neutral position. Currently, i can't provide any negative experience with one, but i want to keep it that way?

[donv]

I have never put the flaps in neutral in a Turbo Commander for parking. Never.

I was curious, so I looked to see what the factory has to say about it. In the 1000 AFM (what I have at home), it says nothing about putting the flaps in neutral. It says "Flaps.... UP" after landing and doesn't mention flaps again.

Under "Flap Control System" in the systems section of the AFM, it says this:

"When flaps are positioned full up or full down, leave the control lever in the UP or DN position. The flaps must be up when checking hydraulic fluid quantity."

Maybe this is a piston Commander thing that someone carried over to the turbines? I don't remember what I used to do in the 500S, but I don't think I brought the flaps to neutral after landing?

[Badger]

OK, Since I was the first to mention "Leaving the flaps in neutral," let me clarify my observations.  I just checked by 500B flight manual and it does say AFTER LANDING: FLAPS - UP. LEAVE THE FLAP HANDLE IN THE UP POSITION. 

So, it appears that I have been doing it wrong for the past 14 years.  I guess I was taught that to keep the Flaps from drooping to bring the lever back to the NEUTRAL position at shutdown.  Thus, that is what I do.  During the times that I failed to do that, the Flaps drooped EVERY TIME.  When the switch is in NEUTRAL, the Flaps never droop for me. 

TAKE-AWAY:  I am doing it wrong, it seems. However, for me (and me alone) leaving the Flaps in NEUTRAL works best.  If anyone knows why that might be a bad idea, or why the Checklist says to leave the lever in the UP position,  please let me know.  Until then, I will continue to set NEUTRAL on the Flap lever after landing.  I don't like drooping Flaps.

I retract my suggestion that others put the lever in the neutral position after shutdown.  I am absolutely NOT advocating going against the checklist.  Up until today, I truly did not realize that the checklist (500B) said to "Leave the handle in the UP position."  I have to admit that I am somewhat baffled....

ed

[kent4142]

I do love a good mystery.  I am scheduled for my 150 hour on the 28th of this month.  I am gong to ask some the Commander experts at Byerly Aviation.  We'll see what they say.

I am still considering whether there is a connection with Maine versus Florida.  In 312 hours of flight I have only had drooping flaps twice - both times and the only times were in Rockland Maine.

I am also going to play around with neutral versus "up" position.

Thanks for the input.

Kent

[Adam Frisch]

I had the opposite problem. On the 520 I was told to keep flaps in Neutral in flight so as to not stress the pump. The gear legs would start drooping immediately and come out into the slipstream. In UP, they stayed up. So I stopped using Neutral. My flaps always drooped in UP as well, but the gear stayed up. She was pretty old and leaky, admittedly.

[donv]

If you are worried about banging your head, just leave the master switch on for a few seconds when you get to the airplane, and the auxiliary hydraulic pump will bring the flaps up, if they have drooped at all.

The first thing I like to do is make sure the battery is good, so I always turn the master on and check the fuel level as soon as I get to the airplane.

[Bruce Byerly]

I’ve found it depends on where all the O rings in the gear/flap selector are happy. Eventually they need to be rebuilt. The late model planes don’t have neutral so it must be ok to leave the handle up though I’ve tended to put it in neutral for aforementioned reasons and it seemed to work better on the last couple of piston planes at least. YMMV. 

[donv]

Ever since I got my airplane painted, the flaps droop over a few days. It used to be that they generally stayed up and only drooped once in a while-- now they always droop.

Any suggestions? Easy fix?

[SKYFLYER]

Must be all the "weight" of that new paint

I have never figured it out as mine sometimes do and then will go for a time and not drop. Used to think it was temp related, but not really any proof of that.

Guess it means you will just have to fly daily to keep them up.  Now that sounds pretty good.

[donv]

It is important to note that the flaps must be up to get an accurate check of the hydraulic fluid level.