B727 flap use above FL200

[Tight Slot]

Air crash investigation last night…

B727, a non approved procedure of extending trailing edge flaps to 2 whilst pulling the leading edge breaker to prevent any slat movement at FL390…?

How on Earth does this give better ground speed as suggested in the program. Maybe delays any Mach tuck?

penny for your thoughts

[Meikleour]

I think they were trying to get more lift out of the wing whilst climbing to a level that really was too high for them to get out of the strong headwinds and thus improve their groundspeed. These drama/documentaries tend to be a big "light" on technical details!

[B2N2]

Increased surface area of the wing allowed a “alternate” (higher) Optimum Altitude therefore better winds hence a better ground speed.

[Tight Slot]

Thanks. Line pilots becoming unqualified test pilots on revenue flights to save a few mins.

[B2N2]

Thanks. Line pilots becoming unqualified test pilots on revenue flights to save a few mins.

Well nobody flies 72’s anymore on pax revenue flights.

[anson harris]

There's an interesting paragraph or two in "Handling the Big Jets" which explains the highly arbitrary nature of the FL200 limitation. And also why the manoeuvre margin changes at that level.

[pineteam]

I’m no expert but what about the drag? Must be noticeable at high speed..

[olster]

With Boeing types the initial degrees of leading edge devices promotes more lift than drag. The well documented 727 incident which nearly ended in catastrophe is more explainable by human factors and stupidity.

[blind pew]

The trident had a droop limitation of fl230 iirc as the flow would become locally supersonic, ignoring it led an involuntary descent through the Clacton hold before the crew could recover the aircraft.
There were a couple of captains that would descend a few hundred feet at cruise level to accelerate the aircraft and allow it to fly with a lower nose attitude would reduce parasite drag and allow a higher cruise or lower fuel consumption.That's the theory they spouted..there is also the ram air effect to take into consideration.

[deja vu]

Thanks. Line pilots becoming unqualified test pilots on revenue flights to save a few mins.
This wasn't the first time it had been done but probably the last.

[megan]

There were a couple of captains that would descend a few hundred feet at cruise level to accelerate the aircraft and allow it to fly with a lower nose attitude would reduce parasite drag and allow a higher cruise or lower fuel consumption.That's the theory they spoutedGetting the aircraft "on the step" was a feature espoused by many old timers flying pistons, Ernest Gann among them. The theory, as I understand it, relates to the drag curve, there are two speeds at which an aircraft can fly with a given amount of thrust, could possibly see the technique working in a thrust limited situation.

[Pugilistic Animus]

There's an interesting paragraph or two in "Handling the Big Jets" which explains the highly arbitrary nature of the FL200 limitation. And also why the manoeuvre margin changes at that level.
Hi Anson...which version of HTBJ are you referring to? I can't find it

[ImbracableCrunk]

Hi Anson...which version of HTBJ are you referring to? I can't find it

It's been 15+ years since I read it, but wasn't it simply that Boeing decided they had enough data and didn't feel like going above FL200 was necessary?

[kenparry]

Never flew the B727, but on the Boeings that I did fly there was a limit of FL200 for flap extension. I believe the reason was simply that no relevant flight tests had been done. This ties in with #13 above.

[HOVIS]

787 has cruise/climb flaps. The inner and outer flaps are physically disconnected by a clutch mechanism, allowing the inner flaps to extend by a few inches to increase performance.

[happybiker]

.which version of HTBJ are you referring to? I can't find it

3rd edition Dec 71 page 170 refers to the use of flaps at high altitude. DPD refers to pilots who have developed a habit of using flaps at altitude which has raised concerns. His primary concern is that flap design is based on their use for TO, climb, decent and landing and will be retracted for the rest of the flight. The strength and fatigue calculations for the flaps are based on this normal use. He goes on to point out that the flight manual limitations for flap use are there for reasons and should be observed.

[dixi188]

I used to fly with an ex BOAC VC10 captain who said there was a trick to improve the climb by splitting the flap/slat lever and doing something to either flaps or slats. When the Trident crashed at Staines the practice stopped overnight.

[extreme P]

There's an interesting paragraph or two in "Handling the Big Jets" which explains the highly arbitrary nature of the FL200 limitation. And also why the manoeuvre margin changes at that level.

​​​​​​Use of flaps at high altitude

It would appear that in recent years pilots have developed the habit of using

their flaps at high altitude, presumably for holding or descent purposes.

This rather indiscriminate use of flaps has caused some concern. While the

captain of an aeroplane can of course take any action he considers justifiable

under a special set of operational conditions, there are good reasons for

not using flaps in other than the normal circumstances.

Firstly, flap design is based on the assumption that the flaps will be used for

take-off and climb, and approach and landing, and that they will be retracted

for the rest of the flight. On this assumption are based the strength and

fatigue calculations of the flaps. If they are used at other times then the

original design assumptions are compromised. Secondly, there is a lower

level of proof strength with the flaps extended; this is quite often + lg

increment instead of the + 1 ½g increment in the flaps retracted case. Lastly,

on some of those types fitted with stick shakers and stick pushers, the

design of these systems is such that, with the flaps extended above certain

altitudes, the shake and the push will not function in the correct fashion and

the aeroplane will be denied some of its normal stall protection (in the clean

configuration stall protection is provided at very high altitude by the marked

pre-stall buffet due to Mach number effect, regardless of the point at which

the stick shaker operates).

In this last instance specific limitations on the use of flaps above certain

altitudes will be found in the Flight Manual. They are there for good

reasons, so observe them. Unless there are specific operational reasons the

use of flaps should be confined to the normal low altitude fun􀁊tion. While

you are about it, do try to stay within the speed limitations; flight recorder

results show far too many occasions on which the flap speeds have been

exceeded, in some cases by large margins.

[Bergerie1]

dixi188, I would like to know how your ex-VC10 captain knew that his special method gave him any advantage. Without doing repeated runs (or climbs) under controlled conditions with and without his special technique, and measuring the difference, there would have been no way he would have known. That is why the industry has test pilots. Does your average line pilot know how to measure performance climbs, etc?

[Pugilistic Animus]

Thank you Extreme P and Happy, found it!

[dixi188]

Hi Bergerie1, I think he said it was to get a better rate of climb when speed restricted on departure. It was over 30 years ago that I flew with him so I may be wrong as to the reason.

[extreme P]

FYI...

* This is taken from the Boeing Airliner magazine:

“Several operators have asked Boeing why the Airplane Flight Manual has

a limitation restricting the use of flaps above 20,000 feet. The reason for the

limitation is simple; Boeing does not demonstrate or test (and therefore

does not certify) airplanes for operations with flaps extended above 20,000

feet.

There is no Boeing procedure that requires the use of flaps above 20,000

feet. Since flaps are intended to be used during the takeoff and

approach/land phases of flight, and since Boeing is not aware of any

airports where operation would require the use of flaps above 20,000 feet,

there is no need to certify the airplane in this configuration.”

[blind pew]

I used to fly with an ex BOAC VC10 captain who said there was a trick to improve the climb by splitting the flap/slat lever and doing something to either flaps or slats. When the Trident crashed at Staines the practice stopped overnight.
DIXI I would presume that you heard of the analogy of a flight engineer and a coachman; also that 90 % of pilots are above average and mine that a far greater percent in management are above average.
On my short stint on the VC10 I came cross one captain who knew more about vertical currents in rocket clouds than PF which resulted in a heavy turbulence check and several serious injuries and another who decided a visit to the airport chapel and a copious amount of prayers would ensure our flight safety which seemed to work although his wife made him live in the garage.
As Bergerie writes we are not test pilots although I have witnessed those in the office that think that it doesn’t apply to them as do their own procedures or the law.
My first lot decided to amend the design philosophies and the test pilots recommendation which left a smoking hole in a field.
There was an infamous DC 8 accident where the captain changed the air brake / lift dumper procedures which had them manually selected on short final, a heavy landing, go around and the wing folding downwind. I had a DC9 51 captain who would regularly stop auto lift dumper deployment on landing and another operate above MMO.
In theory flap selection makes a difference but from one post flying heavy metal with at least 5,000 hours and double that number take offs and mostly successful landings I have played around with stuff that test pilots supposedly do including the modification of aerofoils, control systems and C of G limits to enhance performance. Sometimes I’ve been successful, but it’s been my neck on the line and it’s after a lot of informed reading and discussion.
Enjoy retirement; it was a shame that they did way with your position as it was always a pleasure to fly with an engineer.

[Alex Whittingham]

What this man ⬆ said, totally. It happens most when people fly one aircraft type for years and years, forget how to fly aeroplanes generally, and get wrapped up in the minutae.

[blind pew]

????
Flew 6 types of Jets over 22 years at the same time a few light aircraft and some instructing, followed by ten years of varied gliders, motor gliders, microlights and class A overlapping with 22 years of Paragliders. (30 years of model aircraft concurrently).
The type of flying involving extremely close to terrain with experimental aircraft in marginal conditions lends itself to 110% understanding of the limitations of both machine and man.
As to forgetting how to fly aeroplanes generally..they go where you point them and just in case I ordered a new reserve parachute Sunday.

[Alex Whittingham]

I wasn't clear, I was agreeing completely with what you said

[Checkboard]

In the incident the flaps were never extended. The investigation came up with a silly scenario to explain the departure of the leading edge device because Boeing insisted that the leading edge actuator could never fail. But it was later shown it could fail - and the twisted logic scenario the FAA proposed could never happen.

Every pilot knows that the flaps increase drag. It was shown that "popping" the flaps as propsed indeed increased drag and that anyone who actually tried it in real life would experience greatly decereased performance - as you would expect. The idea that Boeing designed a wing so badly that a pilot "popping" the flaps out would improve performance is laughable - except to the idiots at the FAA.

The Captain who recovered the jet upset after the actuator failure, who should have been hailed as a hero, was pilloried by the investigation for nothing.

[V_2]

The Captain who recovered the jet upset after the actuator failure, who should have been hailed as a hero, was pilloried by the investigation for nothing.

Maybe, but the crew deleted all the cockpit voice recorder data because…?

[john_tullamarine]

Maybe, but the crew deleted all the cockpit voice recorder data because…?

.. because that has been standard Industrial pilot practice for donkeys' years. I would have been astounded had they NOT wiped the record !

(Caveat - I am a bit removed from practical pulling and pushing these days so my comments may only apply to days of yore ? Certainly, in my airline days it was a pretty standard process as the intention was that the CVR only be read in the event of dead pilots. Many crews made it a routine practice to wipe the CVR at the end of every sector. As you might be aware, not all airline management groups are of high moral integrity seeking only the truth of any matter. The only instances I can recall where this was not the practice was where the captain saw fit to use the CVR as evidence for some problem or another and required the unit to be pulled post flight.)

[blind pew]

Apologies Alex.
John I would add wrt cvr that I and another co pilot were set up by a captain on descent into home base with some derogatory comment about a manager and then left the flight deck. We weren’t stupid and communicated by sign and mouthing. On stand I wiped the CVR and was faced with a tirade from said captain.

[V_2]

The only instances I can recall where this was not the practice was where the captain saw fit to use the CVR as evidence for some problem or another and required the unit to be pulled post flight.)

Ok thanks for the insight. perhaps a shame for his own defence, that the Captain/crew decided that losing control and flying inverted wasn’t worthy of being one of those instances.

[dixi188]

Blind Pew, many thanks.
As to the F/E and Coachman, I couldn't possibly comment!
Had one captain on the Electra that thought he should sit in the middle seat as it was a bit higher than the pilot seats and had a better view. He also thought I should be down below stoking.
I'm enjoying retirement.
Dixi

[blind pew]

DIXI;
Instructed for a mate at Blackbushe on the Condor who went on to drive the Electra…AA.
He raved about it having grown up - if he ever did - on Shackletons.
Wasn’t it one of those that did a touch and go at Shannon without the wheels?
There was a short lived movement to do similar on the Trident with the captain on the middle seat supposedly as the Russkies did at the time.

[deja vu]

Ok thanks for the insight. perhaps a shame for his own defence, that the Captain/crew decided that losing control and flying inverted wasn’t worthy of being one of those instances.
Never likely to aid a defence when the crew can provide all information thats needed.

[dixi188]

DIXI;
Instructed for a mate at Blackbushe on the Condor who went on to drive the Electra…AA.
He raved about it having grown up - if he ever did - on Shackletons.
Wasn’t it one of those that did a touch and go at Shannon without the wheels?
There was a short lived movement to do similar on the Trident with the captain on the middle seat supposedly as the Russkies did at the time.

N285F at Shannon operated by Renown Aviation in Channel Express colours (wet lease). 1 March 1999.
I flew on that aircraft during my training with Zantop.

https://aviation-safety.net/database/record.php?id=19990301-0
Dixi.

[blind pew]

They did well to get it back on the ground…remember flying an aircraft that required cancelling the gear horn every time you closed the throttles…iirc Douglas; not unlike the Trident in early days where the droop micro switches were badly adjusted…select them in, cancel the amber attention getters automatically.