Flaps at high altitude airports .

[HoratioWondersocks]

Hello All

Tonight iam flying from Fajs to Fact.

Aircraft is A340.(Posky variant)

Airport altitude is over 5000ft

I selected 15degrees of flaps .

Even giving it full throttle it took an awful lot of runway to get airborne.

Payload and fuel very low as flight only 700 miles or so.

Should I have set lower flap setting(5 or 10 deg or more than 15 deg.

I have had the same problem with same aircraft taking of from Kabul.

Barely making it into the air before nearly running out of runway.

Is this just a quirk of the posky a340 perhaps and nothing to do with my flap settings.

 

Cheers Andy

[mrzippy]

It's always worth a try to add the next flaps setting and see if it helps. Did you add any elevator pitch trim?

[StringBean]

It's all about airspeed.

 

The thinner air at the higher altitude would require a longer takeoff run to achieve enough airspeed for the wings to provide sufficient lift to takeoff.

 

As to the accuracy of the flight model, that is another discussion altogether.

 

Without accurate performance charts (something you rarely see in freeware, let alone payware) that discussion is moot.

 

peace,

the Bean

[ScatterbrainKid]

Pulling back on an airliners stick/yoke seems to have little effect in some cases, but like Zippy said, uptrim seems to do the trick.

If my heavy baby is trundling down the runway and doesn't seem to want to unstick, I jam my finger on the uptrim key and keep it there until the nose lifts and there's daylight under the wheels.

And like guys have said, thin air at high airports means the wings haven't got much to bite into, so experiment with various flap settings and wind speed/direction.

 

PS- KLXV Leadville, Colorado is the highest (9,927') airport in North America and is also used for helicopter testing, so it'd also be good for practising high-alt takeoffs in FS2004/FSX with heavy planes because if you can get out of there you can get out of anywhere..:)

[ronzie]

It is not just altitude but density altitude which is temperature related. The hotter the air the thinner for both engine performance and lift and the density altitude increases.

 

http://carlosneto.org/fs/files/A340PERFORMANCE.PDF

 

should help.

 

Some references for these tables:

https://en.wikipedia.org/wiki/Pressure_altitude

https://en.wikipedia.org/wiki/Density_altitude

[HoratioWondersocks]

Thanks guys

Much valuable I formation.

I did know about thinner air at altitude, but was not aware of the temperature effects having an effect on air density as well.

Anyways in my op I did state that I used 15degs of flaps on my a340 at 5000ft airport height.

I do realise that fs9 is far more forgiving (is it!!) than the real world ,but in the real world , generally would 15 deg of flaps be excessive at any airport height ?what would be the maximum amount flaps an aircraft (airliners mainly in my case) would ever use on takeoff.

As for trimming i never touch it normally, I assume its at a neutral setting in fs(I've never had problems on takeoff after years of flying )so I must be doing something right.

Having said that I have noticed that if for some reason I have inadvertently engaged autopilot on the ground and then turn it off ,the aircraft I am flying will often takeoff by itself having only travelled a short distance down the runway.

Am I right in thinking that having accidentally engaged the AP on the ground it has then altered the trim setting from neutral ,so that even though I have disengaged it ,those trim settings have remained resulting in my STOL type takeoffs.

Anyways back to flaps .What is the maximum amount of flaps an airliner would ever use in the real world .

I generally use 5 to 10 deg for most operations and have no problems with those settings.

Anyways 2

I will try the same try Posky A340 tonight at a nearer sea level airport just to see how it performs with 'normal' 5 to 10 deg flaps .

Thanks for all the help .

 

Cheers

Andy

[dspaulding]

Airlines never use full flap takeoffs. Too much drag if you lose an engine after V1

[mrzippy]

I downloaded and installed the FS2004 SpanAir POSKY A340 from the library and tried your takeoff at Johannesburg Intl. Flaps at 5 degrees, 4 clicks of elevator trim, 95% N1, fuel load at 50% all tanks, and used only about 3/4 of the runway. You drive for show and putt for dough!;) (Lee Trevino) I think!

[StringBean]

What is the maximum amount of flaps an airliner would ever use in the real world?

 

That question is only answerable with- "it depends".

 

Each type will have it's own performance charts and those may vary from operator to operator.

 

Those charts coupled with takeoff weight, density altitude, etc. will dictate flap settings.

 

There is no one size fits all answer.

 

peace,

the Bean

[dspaulding]

I would be surprised if FAA okays full flap takeoffs. Humor me and try it. At MTOW, full flaps, high terrain, engine failed at V1. You will initially have climb performance but will lose it quickly.

[il88pp]

You are right about ap adding trim. You set a high alt in ap-window, so aircraft tries to climb. Using trim to do it.

As it is not having an effect, because you are sitting still, it adds more and more.

And yes, airliners often set a lot of flaps on takeoff.

[dspaulding]

Which ones? Types?

[il88pp]

flaps 20 oftemn used in 747, sometimes more.

 

It's up to the pilot how much flaps he sets. The FAA dos not forbid setting full flaps.

[dspaulding]

Flaps 20 isn't full flaps. A pilot in a transport category aircraft doing full flaps TO doesn't have any margin for error with an engine failure. All the drag plus the weight doesn't seem to equate to adequate climb gradients to meet 2nd climb segment in my mind. Yes I can see a go-around but a takeoff at V1??? Also, a 747/A340/A380, I can possibly see where it's not as detrimental vs 737/MD80, or any RJ. I got to try this when I get back home. Full flap TO seems too dangerous to do with something so heavy.

[ronzie]

AP should not be engaged for an airliner until 1000 feet AGL on take-off. Remember the auto-pilot pitch control uses elevator trim for control. Some aircraft do have a ground contact switch that prevents engagement. Better to use manual anyway.

 

Anyway, that is why it is important to set elevator manual trim so when the AP is engaged it is within AP trim control range.

 

I hand fly using manual pitch maintaning no more than three degrees pitch until 200 feet agl to prevent tail strike then increase to about 12 degrees and then engage AP. Inital MCP heading is set to runway heading and then as ATC or published DP command manually change HDG to conform to desired path. Before I engage HOR path heading control I double punch the top waypoint in the LEGS table so it uses present position to the next waypoint. It all happens fast :)

 

Based on B737 NG series but applies to most jet airliners.

[HoratioWondersocks]

AP should not be engaged for an airliner until 1000 feet AGL on take-off. Remember the auto-pilot pitch control uses elevator trim for control. Some aircraft do have a ground contact switch that prevents engagement. Better to use manual anyway.

 

Anyway, that is why it is important to set elevator manual trim so when the AP is engaged it is within AP trim control range.

 

 

 

I hand fly using manual pitch maintaning no more than three degrees pitch until 200 feet agl to prevent tail strike then increase to about 12 degrees and then engage AP. Inital MCP heading is set to runway heading and then as ATC or published DP command manually change HDG to conform to desired path. Before I engage HOR path heading control I double punch the top waypoint in the LEGS table so it uses present position to the next waypoint. It all happens fast :)

 

Based on B737 NG series but applies to most jet airliners.

 

OK Ronzie

That's pretty much what I do as well.

Particularly with Posky 747s

You have to ease them into the air very carefully or you end up with tail strike and are then lumbered with those horrible smoke and spark effects .

Anyways I may try another flight from Kabul (with the A340 that I've had trouble with )and experiment with manual trim settings before I takeoff (something i never normally do because I have never needed to;my takeofs being trouble free normally)

 

Cheers Anfy

[dspaulding]

AP should not be engaged for an airliner until 1000 feet AGL on take-off. Remember the auto-pilot pitch control uses elevator trim for control. Some aircraft do have a ground contact switch that prevents engagement. Better to use manual anyway.

 

Anyway, that is why it is important to set elevator manual trim so when the AP is engaged it is within AP trim control range.

 

I hand fly using manual pitch maintaning no more than three degrees pitch until 200 feet agl to prevent tail strike then increase to about 12 degrees and then engage AP. Inital MCP heading is set to runway heading and then as ATC or published DP command manually change HDG to conform to desired path. Before I engage HOR path heading control I double punch the top waypoint in the LEGS table so it uses present position to the next waypoint. It all happens fast :)

 

Based on B737 NG series but applies to most jet airliners.

 

Don't know about every airliner. Emb145 limitation is 500' AGL

[ronzie]

Don't know about every airliner. Emb145 limitation is 500' AGL

 

It actually can vary with airline policies as well as aircraft type. Some like more hand flying to build pilot hand flying time to meet FAA and other jurisdiction credits and in some cases to please insurance companies.