dc10
Posts: 122
Joined: Sun Apr 01, 2007 11:53 pm

Take-off With Full Flaps

Thu May 10, 2001 8:38 pm

Hi, what would happend if an aircraft try to take-off with full flaps (because for ex of a pilot error)?
Is there a special alarm in the cockpit?
Is it aerodynamically possible?
Has it already happend?
Thanks!
DC10
 
Guest

RE: Take-off With Full Flaps

Thu May 10, 2001 8:44 pm

I am not sure about Dc-10's however the aircraft I fly (PA-38) is certified for full flap take offs, I only ever do his when doing touch and goes!
Iain
 
OldMan
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RE: Take-off With Full Flaps

Thu May 10, 2001 8:48 pm

If the flaps are not in the take off position you will hear a configuration warning horn as you advance the power. Oldman
 
windshear
Posts: 2261
Joined: Tue Mar 14, 2000 4:45 pm

Hmm

Thu May 10, 2001 10:03 pm

I would think so...
The 767 can make an appropiate take off flap setting of 15 degrees out of possible 30, but if runway conditions restricts the runway length, or when opperating with heavy weight it's totally ok and appropiate to take of with the flap setting of 20 degrees.

To try that with a setting of 25 or 30 doesn't seem desasterous.
At that flap setting you would get a lower V1 and Vr speed, and work quick and hard to retract the flaps at their respective speeds:O)

Please do not take my words to be entirely true, I just can't see any worst case scenario in taking off with a higher flap setting than usual, if a go-around is required it's almost with a full flap setting...
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
bio15
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Joined: Fri Mar 23, 2001 8:10 am

RE: Take-off With Full Flaps

Fri May 11, 2001 3:13 am

The reason why planes don't use full flaps during takeoff, is that the higher lift they produce will implicate an increase in drag, which is unwanted during takeoff. I don't know how serious can a full-flap takeoff be, but typical flap settings are definitely more efficient.

However, full flaps is not aerodynamically impossible to do, as long as you don't exceed the maximum flap speed (which is not likely to occur during a takeoff roll). Oldman is correct, you'll get a warning if takeoff config. is not proper.

-bio
 
chdmcmanus
Posts: 372
Joined: Wed Mar 21, 2001 12:53 am

RE: Take-off With Full Flaps

Fri May 11, 2001 4:00 am

Most acft I have run data for, if you try to take off with flaps full, you will eventually make it airborne, after a very tong T/O roll, due to the drag. The problem comes into play when you loose an engine on T/O, after Vr (Velocity, refusal speed), you normally wouldn't have enough thrust to overcome the additional drag and continue to Vrot (Velocity, rotate), but your too fast to stop in RA (runway available). The result is an unsafe takeoff based on 3 eng takeoff ground roll.
"Never trust a clean Crew Chief"
 
Guest

Iain

Fri May 11, 2001 4:39 am

I also fly the PA-38 but never take-off with full flaps... For touch and goes, once the gear is on the ground I push in the Carb. heat, retract flaps to max 30 and give her full head again... Sounds very strange to me. I was told that everything over 30 is drag and take off distance is increased tremendously...(That's why for STOL take off's one uses 30 and not 45)

Regards: Sven
 
Guest

RE: Take-off With Full Flaps

Fri May 11, 2001 6:56 am

Gyro That's why for STOL take off's one uses 30 and not 45

The flap settings on the PA-38 I am flying is 0, 21, and 30. 45 degree flaps seems an awful lot! The aircraft does fine doing touch and goes with full flaps, the reason we do that over here is becuase most of our runways are very narrow, and with everything you have to do on the ground, many people find themselves going off one side!
It does create one problem you do have to be careful not to wheel borrow it, so you do have to hold some bac pressure!
Iain
 
EssentialPowr
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Joined: Wed Sep 06, 2000 10:30 pm

RE: Take-off With Full Flaps

Fri May 11, 2001 10:10 am

All transport category a/c are certified with certain takeoff flap settings. If a greater flap setting than approved were used, other than a FAR bust, there is a simple reason that the higher flap setting is not certified.

The reason is that second stage climb requirements mandate a specific climb gradient after the loss of an engine. An a/c may be able to perform fine with all engines operating at the higher flap settings, but as was said, the rotation speed would be so low such that, if the engine is lost, the a/c that has minimal kinetic energy. Combine this with the low altitude from the takeoff phase, and the outcome wouldn't be pretty.
That scenario is in effect what defines the take off flap range.

To answer the question, for an a/c like the 727, Flaps 30 is not approved but can be done. Flaps 40 is really almost a "spoiler" flap position b/c it adds tremendous drag; the camber of the wing is so accentuated at the flaps 40 position that the Lift coef is almost the same as FLaps 30 but with much more drag. A heavy 727 has trouble flying level at flaps 40 at high power settings, let alone climb.

Nice question, good responses.
 
OldMan
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Joined: Thu Sep 28, 2006 7:38 am

Windshear

Fri May 11, 2001 9:28 pm

One very good reason not to take off with a setting that is not aproved is this. Here is the worse case scenario you mentioned.

For example a take of with more than approved flaps like Iainhol said give more drag. So you for some fool hardy reason decide to to that and just as you reach your v1 or vr and how would you compute them? You have a engine failure with the gear down and full flaps. There is only one place you are going and that is down. You will be down before the flaps reach a normal setting and should you happen to be a few feet in the air and "think" you will fly and pull up the gear, what happens? The gear doors open and bingo, lots more drag.. Professionals don't wonder abut the "what if's" they stick to the approved program. Regards. Oldman
 
musang
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Joined: Sun Apr 08, 2001 4:11 am

RE: Windshear

Sat May 12, 2001 1:11 am

Ref. take off flaps - The BAe 146/Avro RJ series flap settings are zero, 18, 24, 30 and 33 degrees. The type is approved for t/o at all except zero. We use RJ 100s and our procedures don't cover flap 33 take offs; 18 is preferred, longer t/o run but best climb performance (rate, and noise footprint). 30 gets you airborne sooner but with a degraded climb. Examples of the speeds for the RJ 85 -

For 1000 ft elevation and 10 celcius temperature, at 43,000 kg -

Flap 18 Vr is 133 knots, V2 is 141.
Flap 24 Vr is 125 knots, V2 is 130.
Flap 30 Vr is 118 knots, V2 is 123.

I don't have the data for flap 33.

Retraction from 30 to 24 is at V2+10, i.e. 133 knots, 24 to 18 at V2+20 i.e. 143 knots, and 18 to zero is at Vfto, the Final t/o speed, which for 43,000 kg is 188 knots

Flap 30 is required for certain short runways, and for contaminated runways (slush, snow, patches of water etc.), which you definitely want to escape quickly as the contaminant drag increases exponentially as a function of groundspeed.

In my early days as a student pilot I had a flap fuse failure on a touch and go in a Cessna 150 with 40 degrees flap (later versions only had 30 for safety reasons). I carried on because inexperience made me neglect to visually check the flaps were retracting, until too late, insufficient room to stop. The highest I got on that circuit was 350 feet!

Regards - Musang
 
windshear
Posts: 2261
Joined: Tue Mar 14, 2000 4:45 pm

RE: Windshear

Sun May 13, 2001 10:47 pm

I totally agree with Musang & Oldman, what I ment was that although the pilots do not have the data cards for such high flaps settings, it would not be a disaster if the pilot "forgot" (it can't happen, really it can not occur!!!) the rate of climb would be low and AOA (Angle Of Attack) would be high, but the powerful engines on both the DC-10 and the 767 would give it the push and acceleration needed to stay airborne.

What I then wanted to state was the rate or as I put it, hard work needed to raise the flaps at their respective V's...

I would have to disagree with the drag rate for resulting in an actual increase of runway length needs...

I also did point out which setting was prober, meaning allowed...

SO there you have it: it's braindead to try such a takeoff, as every planning you made for climb would be false and also for the fuel quant. calculations for the entire trip would be of no use.
It's unwise to puch or try something not allowed by the manufactorer...

So stick to the data files that went with the aircraft, and you'll be safe:O)
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
chdmcmanus
Posts: 372
Joined: Wed Mar 21, 2001 12:53 am

RE: Take-off With Full Flaps

Mon May 14, 2001 1:45 am

I would have to disagree with the drag rate for resulting in an actual increase of runway length needs...

The definition of critical field length is;
"The total length of runway required to accelerate on all engines to Vcef (critical engine failure speed), experience an (1) engine failure, then continue the takeoff or stop."
There are a number of factors affecting the ability of an acft to accelerate, drag being one of them. As you follow the L/D graph for flap settings on a chart, you will realize that at some point, depending on mfr, the flap's coefficient of drag will begin to increase as the added lift stabilizes. This increase in will reduce the acceleration rate for Vrot (V1) and increase the length required for takeoff. When the CFL is longer than the runway available, it is an unsafe takeoff. Alternatively, if Vref (Go speed) is greater than Vrot (V1), you have a "split marker" takeoff. While performing a split marker TO, after Vr you are committed to takeoff, and any emergencies must be handled in the air. If you loose an engine, you can still take it airborne based on Vcef and CFL in the RA (runway available). However, if the L/D on the flaps is the D (full flaps), your CFL will increase unbelievably due to the remaining engines having to overcome the unnecessary additional drag, and in some acft, you will simply never reach Vrot (V1). Thus in both cases additional runway length will be required to perform a safe takeoff. The acft I am currently flying (L-300) has published procedures for 3 engine T/O, and 0 Flap T/O, but if we have flaps 100, our CFL to make Vrot (V1) on 4 engines is off the chart, let alone 3, and most of the other acft I have been trained on were the same way. The reason acft are able to use full flaps on approach and go-around without the same problem is the momentum-thrust relationship known as the “power curve”, which is a whole different ballgame on takeoff.

Also, as far as (it can't happen, really it can not occur!!!), you should definitely read the accident reports for crashes after takeoff in which the acft was not properly configured, there are a lot of them.

Regards,
ChD
"Never trust a clean Crew Chief"
 
EssentialPowr
Posts: 1646
Joined: Wed Sep 06, 2000 10:30 pm

RE: Take-off With Full Flaps

Mon May 14, 2001 11:44 am

As I stated, using anything other than what the a/c is certified for is foolish and certainly an FAR bust in the best case scenario.

The point is made that, from a theory standpoint, a takeoff using greater than certified flap settings for about any transport category a/c is a potential disaster. ANY transport a/c 767, DC10, 747-400, A320, ERJ - using full flaps for take off at heavier weights will probably end up in the weeds. These a/c are much more heavily wing loaded than a general aviation a/c like a PA 28, and aren't designed or capable of having "the push and acceleration" to prevent a disaster at middle to heavier weights/full flaps. Again, a middle weight 727 has trouble climbing at all at flaps 40 (in the Sim) at typical approach speeds.

As was said, improper take off configurations have killed many people in the last 20 years.

Cheers
 
762er
Posts: 522
Joined: Thu Feb 08, 2001 8:18 am

RE: Take-off With Full Flaps

Mon May 14, 2001 3:23 pm

At the Kahului, Maui international airport (PHOG, OGG) the runway is less than 7,000 feet long. Hawaiian, ATA, United, Canada 3000, and a few others operate daily DC-10-30s, L1011's, 777's(earlier), and A330's to the west coast. I can understand how these planes would be fine taking off on this runway because they aren't loaded up with fuel which means the required runway length is less (I think). However TWA and American operate daily 767-300's to STL and DFW respectively. These planes are loaded up with fuel and often operate with max pax capacity. Is it safe for these planes to take off with such little room to spare? Do these planes use higher flap settings in order to get airborne faster. I've been on the TWA flight several times and was surprised when they didn't lock the breaks and apply power but took off normally. An AA pilot who flew the 0GG-DFW route told me he held his breath during every take off roll at OGG. I'd like to hear what you guys think of this.
 
Guest

RE: Take-off With Full Flaps

Mon May 14, 2001 8:29 pm

Chdmcmanus,

Interesting explanation, I presume that the terms which you are using (Vrot, Vcef) are USAF terms?

767er,

In this day and age, the majority of takeoffs are based on using the complete runway, if the aircraft is not limited by the takeoff weight, the actual takeoff thrust will be reduced to use all the runway, which provides engine savings to the airline. Therefore what you are seeing in Kahului is not only safe, but common.

Crews have a number of options regarding takeoff flaps, some will give better runway limited weights and slower speeds on shorter runways, others will provide better climb/obstacle clearance. You may find that on short runways, a higher flap setting is selected to give a lower V1.

Rolling takeoff versus static takeoff, there is very little in the difference in actual takeoff distance. Boeing allow you to use either.
 
chdmcmanus
Posts: 372
Joined: Wed Mar 21, 2001 12:53 am

RE: Ambasaid

Mon May 14, 2001 10:29 pm

Yes, they are still used by the USAF, It's known as the "go speed" concept. All of the numbers are the same, the only difference is the Pilot calls "Go", "Rotate", "Climbout", and "Flaps" instead of "Go", "V1", "V2". The airlines used to use this system a long time ago, not sure why it changed.

Regards,
ChD
"Never trust a clean Crew Chief"
 
musang
Posts: 788
Joined: Sun Apr 08, 2001 4:11 am

Kaui T/off

Tue May 15, 2001 1:08 am

Any co-pilot who tells a passenger he holds his breath on take off is a bit of a public relations disaster area, but more interestingly doesn't seem to understand, and therefore trust the way take off performance is calculated. The margins are considerable.

Regards - Musang
 
windshear
Posts: 2261
Joined: Tue Mar 14, 2000 4:45 pm

RE: Take-off With Full Flaps

Tue May 15, 2001 5:28 pm

I do not think that using the entire runway length is widespread, it's used at major airports as a way to coordinate traffic flow to be more efficient. I know that the KJFK intl. does this and mentions this in their ASIR charts, almost as if was a law at JFk, but I think it's just after landing, I think that they let them takeoff as quickly as possible...

In OGG the traffic intesity is much lower, and that's is not why they almost scratch the threshold at takeoff, the runway is simply short.
I would say that the 767's would use a flap setting of 20, as this would be sensible in terms of Vr speed and thrust needed.

Honestly to takeoff with a lower thrust setting as put by AMBASAID is insain on such a short runway, to lower the stressfactor on the engines and risk or even cause an accident.
The DC-9 and 737's that fly he interisland routes also have to use max.thrust in order to not risk running out of runway, so to use the entire runway lenght in this case is not by choice, more out of need.
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
T prop
Posts: 912
Joined: Tue Apr 03, 2001 4:33 pm

RE: Take-off With Full Flaps

Tue May 15, 2001 6:48 pm

Windshear,
You mention that Hawaiian and Aloha use max thrust out of OGG, I don't know about that but Hawaiian definitely uses max out of MKK.

MKK's runway 5, the longest, is 4494 feet long with rising terrain at the end, I'll bet it looks shorter from the cockpit!

T prop.





 
windshear
Posts: 2261
Joined: Tue Mar 14, 2000 4:45 pm

RE: Take-off With Full Flaps

Tue May 15, 2001 8:56 pm

T prop It's SO true I think Lanai is even worse, but Molokai has a runway facing a mountain, scary:O)
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
Guest

RE: Take-off With Full Flaps

Tue May 15, 2001 10:21 pm

OK Windshear, as you have said that the assumed thrust thrust reduction procedure or the derated thrust reduction procedure are insane on 7000 feet runways, I would be obliged if you could substantiate your comments.

As for not using the whole runway for takeoff calculations which involved reducing takeoff thrust, I think that you really have to check out what airlines are actually doing!

 
windshear
Posts: 2261
Joined: Tue Mar 14, 2000 4:45 pm

RE: Take-off With Full Flaps

Tue May 15, 2001 11:08 pm

OK AMBASAID RELAX.

I really do not want to hear that kind of crap...

Please I'm not up to fighting with you over this...

I did not say that you lied or anything like that, I only spoke of the airoprts I knew for sure JFK, OGG and CPH.
The rest I'm totally off my field. If airlines are doing it, well that's not unimaginary and I do not want to not believe on this, but reading the ASIR's of JFK they ONLY speak of landing aircrafts having to use the entire runway length.

At OGG The simple fact of runway length speaks for it self...

CPH I can see can't I?!!

Sorry if I crossed your path here...
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman
 
Guest

RE: Take-off With Full Flaps

Wed May 16, 2001 12:52 am

Windshear,

You really have to be careful about passing comments on things that you dont know about.

We had a similiar discussion about reduced thrust takeoffs from PHX, i showed UA documents which showed that over 90% of their flights were operated using reduced thrust, the % on the larger newer aircraft was even higher.

One of the takeoff limitations of modern jets is the accelerate stop, this is the aircrafts ability to accelerate to V1 or Vef (depending on certification date), suffer an engine failure and come to a stop by the end of the runway using brakes and aerodynamic stopping forces, no thurst reversers.

This isnt the only takeoff limitation, but it is one of the major ones. Its therefore extremely easy for me to say that takeoff calculations use all the available runway, all that i have to do is check the field length limit weights. But for you as an observer, you wont have seen that many engine failures at V1 when the aircraft is field length limited, so regardless of what you actually see with your own eyes in CPH, it doesnt tell you what is actually going on!

Now say that the outside air temperature is 20C, and you are doing a max takeoff weight in a B744 from JFK, that aircraft, you could find that you would be able to takeoff if the temperature was 40C at the same weight.

So why use all the available engine thrust? You can fool the engines into thinking that the outside temperature is 40C, they will therefore produce the corresponding thrust.

This policy can apply on long runways or short runways and with just about all aircraft types!

If I'm wrong, you will see the results on CNN at around 9.30 pm New York time, but trust me I hate swimming  Smile

 
windshear
Posts: 2261
Joined: Tue Mar 14, 2000 4:45 pm

RE: Take-off With Full Flaps

Wed May 16, 2001 5:03 am

I never disagreed on any of the things you told, I said that you're proplably right about this, I meerly explained that the only place I had that i writing was on a ASIR page from JFK.

The other thing was the OGG, where such an ettempt would be fatal, but if you use runway 13L/31R at JFK then use that method by all means:O)

I know about fooling the engines and so on, it's briliant aslo I think it's a good thing to relieve the engines from any stress what so ever...

I never disagreed with any of your comments, only in the OGG situation, where it isn't possible, when the DC-9's have to use max TO thrust.

So there we have it guys we agree :O)
"If you believe breaking is possible, believe in fixing also"-Rebbe Nachman

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