Question for MD/DC-9 drivers.

[Singlecoil]

Anyone who has flown this airplane knows that if you go to slats extend, you get a serious balloon effect when you subsequently go to flaps 11. The usual cure is to move the flap handle very slowly to mitigate the rapid change in center of lift when the flaps are extended with the slats at mid.
However, it seems to me the Douglas engineers thought around this and designed the airplane to be configured from clean to slats mid/flaps 11 simultaneously. If the handle is moved from clean to the 11 position without stopping at the 0 position, the slats and flaps come down together, keeping the center of lift in relatively the same station on the wing.

At least that has been my take on it. I flew with a Captain recently that wouldn't comply when I asked for "Flaps 11" from the clean configuration. I had the approach and pattern planned to keep the throttles at idle until 500-1000 ft agl. The speeds for flaps 11 and slats mid are both .57/280, but the Captain said it was "really bad" to do that and "there is a reason" why we don't do that. I had never heard that before, and was unable to uncover a reference in the manual for not configuring slats and flaps simultaneously.

Does anybody else have an opinion on that one? To me, those Douglas engineers were extremely crafty. I don't need to see it in a book to tell me that the aircraft was designed to be configured in the matter I describe. When another captain first showed me you can configure that way without the balloon I had a "Eureka" moment. Clearly the airplane must have been designed with this in mind.

Am I wrong?

 

[airbaker]

Singlecoil,

I've got over 1500 hours on the MD-80 and I used to employ that technique all the time. It was in fact suggested as "technique" during my IOE by very senior check airman. I don't recall there being a liability to going straight to Flaps 11, but I could be wrong. The only time I wouldn't go right to flaps 11 is if I knew ATC was running long downwinds or delay vectors and didn't want the drag/fuel penalty. The 80 had such a strong porpoising effect with the long arm between the center of gravity and the front of the airplane, that I'd try every trick in the book to dampen it for the folks. (another trick was to vert speed it -200 for the initial descent before hitting ias or you'd get a real roller coaster)

 

[Singlecoil]

Thank you, airbaker. I'm glad to hear that. It fully sunk in for me the other day when I was dead-heading and sitting over the wing. When the flaps were moved to 11 at the beginning of taxi, I noticed that the flaps and slats moved in perfect synchronicity (with apologies to the police), that can't be a coincidence.

 

[atldc9]

On the DC-9-30, we used to go to slats and 5 degrees of flaps all at once to avoid the porpoise. It worked very well.

On the 717-200, there are the same tendencies to porpoise, but most times we do the slow lowering technique so as not to have a lot of drag out there. The first flap setting is 13 degrees, a bit too much, unless you are getting the slam dunk short approach off the downwind into ATL.

 

[nhbizz]

Singlecoil,

As was already stated, I agree with that technique as well. In over two years of flying the plane I saw the technique used lots. I adopted it once I flew with a senior IOE airman and asked him about it and he said it was fine to do. I could find nothing against it in any of my companies manuals, but then again maybe I missed it.

 

[justApilot]

Singlecoil...

I have heard of this being a technique. I have also heard that it was common at Reno. My advice is to brief anything outside of SOP's. And out of curiousity what was the Captains' explanation of why this is "really bad"/"there is a reason" why we don't do this?

 

[NuGuy]

Hi all,

At our shop, on the DC-9, no one extends slats and flaps zero unless they need to come down like a safe with the speedbrakes out.

Almost everyone goes slats extend/flaps 5 for the first call, and if the weight/speed is good, sometimes slats extend/flaps 15 if the set up is right for a short approach.

I've flown with a few guys that always had a pet peeve like what you describe. You do something that everyone else and their brother does (including the training department), and the dude goes haywire telling you that it's not allowed/not sop/bad for the airplane/whatever.

Usually, after we're on the ground, I will ask to see the appropriate limitation/SOP page/FOM page, and after a furious search, the guy can't come up with it, and gets even more pissed because "they moved it, besides you should know that".

After asking a IOE guy or instructor, turns out whatever issue was never a limitation, only a recommendation, and besides, it was deleted 10 years ago because it no longer applied.

Some guys are so desperate to show their "knowledge" they get wrapped around the axle. "Insecure authority", I think it's called. If these guys would relax for 5 seconds they would be much more fun.

As always, your mileage may vary...

Best,
Nu

 

[teedub]

slats first

I agree with all about going to flaps 11 as a technique and also about the "insecure command" types around.....for the md80 I would only suggest that extending the slats first and waiting for the blue TAKEOFF light to illuminate eliminates the potential for a combined slat/flap asymmetry......in other words if you get an amber DISAGREE light when selecting slats only then a slat asymmetry exists which can be delt with as an isolated issue with the knowledge that no flap asymmetry exists.....I recall being given a slat asymmetry in the sim. Returning the slat handle to retract was one less step than going from a flaps 11 asym to slats extend to obtain zero lateral trim change...The checklist we had at TWA covered both situations under one proceedure but those are my thoughts on the topic.......

BTW has anyone flown the dc9-30 and landed without arming the spoilers?........wow!! what smooth landings can be achieved..

cheers & warm beer

 

[Singlecoil]

This first captain never could or would tell me what the big hairy deal was.

I flew with a check airman today and he said he had never heard of any limitation associated with slats and flaps together.

Thanks for the replies.

 

[Vortilon]

We used both techniques on the MD88....just depended on who you flew with. I liked the slow & smooth to 11 technique myself but if a captain wanted the other, no big deal...it did work pretty well.

As for your captain not wanting to do it, its nice to be able to refer to something concrete for his reasoning, but in the end it is his/her airplane and as a good, professional FO you have to suck it up sometimes. One day it'll be your call...

Sure do miss the Douglas Death Tube!