Config changes @ low alt

[Zeffy]

During a recent sim session, the instructor criticized my call for a change in flap setting (flaps-2 to flaps-1) during climb below 1500 AFE.

"Danger of flap asymmetry... bad technique... yada, yada..."

We were in a high performance takeoff situation -- plenty of gradient, the airplane was accelerating even with the deck angle ~18-degrees.

I just shut up and responded with "yessir, yessir, three bags full, sir"... while thinking to myself, "What's the first thing this guy will want to see following pitch and power application during a go-round from 50 feet?

If there is a solid rationale (beyond "we've always done it that way") for prohibiting a reduction in trailing edge drag with all engines running under high performance conditions, I'd love to hear it -- especially including any differences between bizjet types and large airliners.

<Shields up...>

[8846]

Yep - I'd heard this before, I am NO expert, just a regular joe-blow fokker driver but it was always explained to me that any change of config. at low level (in a departure situation) could lead to instability and erode safety margins. It's a valid point.

As with so many 'big airline' philosophies - it's designed to produce a 'mind set' that every single one of the 1000+ employees(pilots) will adhere to. We can all be 'artistic' with how we handle an aeroplane - the greater the skill the greater the level of 'artistry' but for a big airline this is frowned upon.

That is my take on it. I think that the skill in airline flying is to do everything in a boringly predictable way but to enjoy ourselves within that framework.

I regularly fly with extremely experienced ex-fast jet pilots who could no doubt do all manner of things with the aeroplane but just do the same boring old stuff day after day - exactly the same way every time.

How does that sound?

[Feather #3]

Most intriguing. Just when DID he say you could make the config change?

IATA came up with a minimum of 800' and our Boeing is programmed to start cleanup at 1,000'...........how long is a piece of string? Equally, as you say, what about the go-around?? But then "Don't mention the War!?"

G'day ;)

[AirRabbit]

8846, that sounds just about right! Once its determined that “the boss” is allowing a deviation from “standard operating procedures” it could easily be like the proverbial “crack in the dam” - and being from Amsterdam, I’m sure you understand the analogy! No one wants an airline of "cowboys," where everyone is doing his or her own thing!

The primary reason for the flap change in a “go-around” situation is to relieve the greater percentage of drag vs. the lesser percentage of lift with landing flaps selected. While any flap extension will gain both lift and drag, generally, the first few stages of flaps provide a much greater increase in lift than in drag, and generally, the final stage (or two) of flap extension provides a much greater increase in drag than in lift. When executing a go-around, you want to get rid of as much drag as possible, without decreasing the capability of generating lift beyond a reasonable amount. But when on departure, going from, say, flaps 5 to flaps 2, while it does decrease the drag, it also decreases the lift, but to a much greater detriment - i.e., a lot less lift as compared to very little less drag.

In the situation described by Zeffy it probably didn’t hurt the performance of the airplane too drastically by going from flaps 2 to flaps 1, under the conditions he cited, but, it did reduce the “vertical climb vs. ground covered” performance of the airplane. I would have critiqued the decision just as Zeffy’s simulator instructor did, and I probably would have used the same “danger of flap asymmetry” comment; but I think I would have probably said “not company policy” or gone into a bit more of the “factual circumstances,” rather than use the term “bad technique.”

[OPEN DES]

Zeffy,

Just wondering.

From flaps 2 to flaps 1 below 1500 AFE, you said. I suppose an Airbus FBW. What was your flightphase i.e. what was your acceleration altitude?

You said that you deck-angle was still 18deg, I am guessing that you were still in SRS-mode (below acceleration altitude) at which point a flap retraction is NOT appropriate regardless of airspeed and acceleration.

[Zeffy]

No, not a 'bus -- an F900 bizjet. (49,000 MTOW, the sim was loaded to about 36,000 lbs)

Both S/F-1 and S/F-2 (Slats + 7-deg and Slats + 20-deg) are approved takeoff settings. S/F-1 provides better hot/high performance (second segment).

The default accel height for the FMS is 400 AFE, but is pilot-selectable.

The top of the SID was 2000 MSL from a near SL airport.
http://www.naco.faa.gov/d-tpp/0706/00890TETERBORO.PDF

I was respecting the crew operating advice not to change config below 400', but didn't see any advantage to dragging the extra flap all the way to 1500 AFE, especially with a light airplane in cool temps.

Also, be mindful that this is a busy terminal area, and zoom-climbs to 2000' may cause RA's for traffic inbound to EWR.

FWIW, auto-thrust is not selectable in this airplane until the wing is clean (however, the throttles work just fine :))

So, I really wasn't at all concerned about sinking into an obstacle -- to the contrary, the primary concern was avoiding a level bust while respecting the 200-kt speed limit below the Class B.

[PPRuNe Towers]

As you've now mentioned it was a Falcon can I ask if the instructor ( you didn't say examiner) was an active, working pilot? Experienced former one? Someone from your own company?

I only ask as responses from european airline guys may be based on the essentially in house world they know rather than that of bizjets and third party sim trainers.

Rob

[PEI_3721]

Sounds like a poorly conceived SOP. Flap asymmetry in any JAR certified aircraft should be a very remote case; it should not happen of if it does, the flaps should freeze.
Check the tech issues. Discreetly suggest that the SOP is inappropriate and encourages violation (MOR / CHIRP).
What happens with an engine failure? Flaps are selected at low altitude; is the risk accepted – why, etc, etc; illogical argument somewhere.

[Zeffy]

As you've now mentioned it was a Falcon can I ask if the instructor ( you didn't say examiner) was an active, working pilot? Experienced former one? Someone from your own company?



Hello Rob,

The instructor is/was not actively flying the type, nor did he have any significant line experience on the type.

How a gov't-approved, third party trainer comes to offer the services of such a person while demanding those eye-watering payment$ from their clients is probably best left to a separate thread. ;)

In the interest of providing additional context for those unfamiliar with the little tri-motored Falcon, the airplane isn't exactly an MD-11... it's quite comfortable maneuvering at the weight in question in a clean-wing configuration at 170 knots... in fact the S/F-1 max speed is 200 kts.

I'm trying to learn more about how/why SOP's and operating guidance are developed as well as differences between certification climb profiles vs. SID/obstacle clearance profiles vs. NADP's etc.


Z

[411A]

The type I fly (L1011) has superb flap assymetry detection, and if signaled, the flaps/slats lock in place, and you have to come back and land.

Another scenario, depending on the operator.

Flap 18 takeoff for shorter runways...select flaps 10 at 400 AAL.
Clean up at 1000 AAL.

-or-

Flap 18 takeoff, and leave 'em at 18 'til 1000 AAL, then clean up on schedule.

Operator dependant.

Looking back even further with older types, the B707 used flaps 14 for takeoff, and they were absolutely positively never to be retracted in a turn, regardless of aircraft altitude.
A Boeing recommendation.

Quite frankly, I see no reason why flaps cannot be retracted at lower altitudes, provided the proper speeds are present, and obstacles are not of concern.