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Yet More Takeoff Distance Question(s)  
User currently offline3DPlanes From United States of America, joined Apr 2006, 167 posts, RR: 0
Posted (7 years 6 months 1 day 3 hours ago) and read 3702 times:

Having read through previous posts, AND having downloaded the Boeing performance docs, I still have some questions about takeoff performance for large aircraft...

In my POH for a Warrior or 172, there are charts for calculating takeoff roll and required distance to clear a 50' obstacle. You enter the charts using temperature, go up to pressure alt, then over (and maybe down) to weight, then over (and up or down) for wind - ending up with the distance.

The Boeing charts are similar, but there are only two charts - one for standard and one for +15c.

Having flown into short grass strips with trees on all sides eek , I know that GA is different... And I understand that large aircraft fly into known airports (usually), hence they already know the runways are long enough, and that if the temp gets hot they can reduce fuel or cargo to get within the available length.

But where do they get numbers or data for abnormal conditions? Like when it's +35c in Pheonix? Or when you land your A320 at a closed field in Ireland? Does that come from the FMS? Does each airline work out it's own numbers, based on their SOPs? (Although the airline flight manuals I have access to don't have these charts in them.) And the Boeing docs from their site are for airport planners, not pilots/dispatchers...

What about bizjets? A G-V or Citation X could be asked to fly into nearly any field the client/owner wanted. Do they have charts to work things out?


"Simplicate and add lightness." - Ed Heinemann
33 replies: All unread, showing first 25:
 
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 1, posted (7 years 6 months 1 day 3 hours ago) and read 3690 times:

Quoting 3DPlanes (Thread starter):
hence they already know the runways are long enough

In real-world airline flight operations we approach it somewhat differently. We don't care what the takeoff roll is going to be. Our interest is how much weight can we lift under today's conditions and still meet all the legally mandated excess performance criteria.

Quoting 3DPlanes (Thread starter):
The Boeing charts are similar, but there are only two charts - one for standard and one for +15c.

I don't know what charts you are looking at but I have Boeing 737-300 takeoff charts for a number of different airports right in front of me. They have a seperate weight limit line for temperatures about every two degrees or so from minus 30°C up to plus 52°C even though the engines were flat-rated to fifty.

On-line airport ("Regular" airports in our ops specs) we have these charts (unless we are using performance computers) If we intentionally fly into an off-line airport for a charter or something the company will get us the charts for those runways. If we have an emergency and land at some place really wierd we will not take off until the charts are in our hands.

By the way, since you mentioned PHX and +35°C my chart says 117,400 lbs would be the takeoff limit based on "climb" and not "runway" restrictions. Ths is at Flaps 5, packs Auto. If I needed to lift more out of PHX on this day I might have access to a "Flaps 1 Improved Climb" chart that could give me a bit more weight capacity in that configuration and procedure.

But again, I just don't care about the ground run. Runway length is fixed, the temperature and winds and anti-skid status are what they are - allowable takeoff gross weight is THE variable.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 2, posted (7 years 6 months 1 day 3 hours ago) and read 3688 times:

Quoting 3DPlanes (Thread starter):
What about bizjets? A G-V or Citation X could be asked to fly into nearly any field the client/owner wanted. Do they have charts to work things out?

These are mostly operated under Part 91 where airlines operate under the more restrictive Part 121. Part 91 operators get almost no FAA supervision at all, as compared with airlines, and the safety record of any given corporate flight department is pretty much up to their pilots. It takes some courage to say: "I'm sorry sir, this plane can't do that." to your boss. Especially when some other pilot has already done it for them.

It is why I would rather drive a truck than fly corporate.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offline3DPlanes From United States of America, joined Apr 2006, 167 posts, RR: 0
Reply 3, posted (7 years 6 months 21 hours ago) and read 3608 times:

Quoting SlamClick (Reply 1):
I have Boeing 737-300 takeoff charts for a number of different airports right in front of me.

That seems to be the rub - I haven't seen charts for a specific airport.

What you explain makes sense. It would be like taking a grass field near me with 2500' available and (knowing the field elevation) working out the max weight for a number of temps, where I could still takeoff from that field. I don't care how much runway I use, just as long as I can takeoff and clear the trees at or below a certain weight - based on the temp.

But, what about baro pressure? Wouldn't a low pressure system change the mix? Or is there enough margin built in? Basically, I'm wondering about density alt.

The GA charts work out density alt by figuring it during the mix. I don't have to calculate the actual value - just start at the temp and go up to the pressure alt for the field that day, and thereby work from a density altitude "value" (disregarding humidity), even though I don't know the actual number.



"Simplicate and add lightness." - Ed Heinemann
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 4, posted (7 years 6 months 20 hours ago) and read 3602 times:

Quoting 3DPlanes (Reply 3):
I haven't seen charts for a specific airport

They are probably not available for free. What might be is a "runaround graph" or "web of death" type graph chart for the generic calculations, without considering runway-specific factors such as obtacles but they would probably have runway slope, wind and temperature skews.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineAirWillie6475 From United States of America, joined Jan 2005, 2448 posts, RR: 1
Reply 5, posted (7 years 6 months 14 hours ago) and read 3541 times:

Quoting 3DPlanes (Thread starter):
one for standard and one for +15c.

15c is standard temperature.


Airlines is not much of a problem. Everything is worked out for the pilots they just basically confirm the info sent by the company, all they have to do is fly. It's more challenging for charter/biz operators. Those pilots actually have to familiarize themselves with all aspects of the trip because they are basically the only ones responsible for the safety of the flight. Often times they fly into uncontrolled airports, remote fields they have to be a little more prepared. Not hard work just more work.


User currently offlineZeke From Hong Kong, joined Dec 2006, 8861 posts, RR: 75
Reply 6, posted (7 years 6 months 13 hours ago) and read 3537 times:

Quoting 3DPlanes (Thread starter):
But where do they get numbers or data for abnormal conditions?

At our airlines we stopped working things out in the cockpit, too many accidents (like SQ in NZ out by 100t on takeoff mass, 747 in Halifax with the mass from the previous sector) are occurring as people make silly mistakes under time pressure.

We just load the mass, QNH, runway, runway condition, MEL/CDL items and temp in ACARS, and the performance computers/engineers back in the main office send us back a message back via ACARS with our speeds, flap, and derate/reduced thrust.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 7, posted (7 years 6 months 13 hours ago) and read 3522 times:

Quoting SlamClick:
If we have an emergency and land at some place really wierd we will not take off until the charts are in our hands.

Unless that place is a levee in New Orleans, presumably.

I guess by definition, the guy who flew that plane out of there was a test pilot...



Todos mis dominós son totalmente pegajosos
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 8, posted (7 years 6 months 9 hours ago) and read 3491 times:

Quoting Zeke (Reply 6):
are occurring as people make silly mistakes under time pressure.

ah, yes never let pressure to go make you hurry and make mistakes.

Quoting Zeke (Reply 6):
We just load the mass, QNH, runway, runway condition, MEL/CDL items and temp in ACARS, and the performance computers/engineers back in the main office send us back a message back

we just input that info into the PAT onboard and it generates the data.


User currently offlineA389 From United Arab Emirates, joined Jan 2005, 59 posts, RR: 0
Reply 9, posted (7 years 6 months 7 hours ago) and read 3458 times:

The numbers you're talking about are FAR take off (other charts for landing) runway length requirements used for runway planning purposes. As you said they are for ISA conditions (15C, sea level) and generally for ISA+15C.

If you want to use then in different conditions you have to correct them (up to a certain extent) for different temperatures, altitudes, runway slopes, etc.

Also when determining the runway length for an aerodrome you need to consider types of aircraft/range/frequency, access possible stop or clearways, costs, etc and you end up with a runway length or better with declared distances.

Those are then used on a case by case basis to determine specific conditions for each operation (weather, loads ...)

Regards
A389


User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 10, posted (7 years 6 months 6 hours ago) and read 3451 times:

Quoting BAe146QT (Reply 7):
Unless that place is a levee in New Orleans, presumably.

I guess by definition, the guy who flew that plane out of there was a test pilot...

I don't know what you are referring to. My post, however, was only about airline operations and actual revenue flights.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineMiamiair From , joined Dec 1969, posts, RR:
Reply 11, posted (7 years 6 months 5 hours ago) and read 3431 times:

Quoting SlamClick (Reply 10):
I don't know what you are referring to

I think he is referring to a TACA 737-300 that had a double flame out and had to land on a levee.


User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 12, posted (7 years 6 months 4 hours ago) and read 3395 times:

Quoting Miamiair (Reply 11):
I think he is referring to a TACA 737-300 that had a double flame out and had to land on a levee.

Yessir. I'm afraid I was overcome by the desire for dry humour.

It was kind of relevant though, since it addresses the question of "What do you do when the figures just aren't available?".

The answer, one supposes, is that you calculate, then calculate again. And once you've done that, you get someone else to fly the damned thing.

Actually it occurs to me that this sort of thing must be quite common in some parts of the world - especially where the gravel deflector is used as a matter of course. And I'll bet the T-43 pilots have some stories to tell...



Todos mis dominós son totalmente pegajosos
User currently offlineKELPkid From United States of America, joined Nov 2005, 6343 posts, RR: 3
Reply 13, posted (7 years 6 months 3 hours ago) and read 3387 times:

Quoting 3DPlanes (Thread starter):
What about bizjets? A G-V or Citation X could be asked to fly into nearly any field the client/owner wanted. Do they have charts to work things out?

Part 91, usually. I would imagine that they must compute an accelerate-stop distance, at least...even piston twin drivers must do that one. Helps determine the point at which you are committed to a takeoff, and at what speed you would be able to safely stop on the remaining runway...



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 14, posted (7 years 6 months 3 hours ago) and read 3386 times:

Quoting Miamiair (Reply 11):
a TACA 737-300 that had a double flame out and had to land on a levee.

Sorry, never even heard about that event. (Guess I need to lurk in Civ/Av more  Smile)

I have no idea what they did to retrieve their airplane. Don't know to what extent the US FAA would involve themselves in a "foreign" embarassment. I expect that cranes and barges might have been involved in the recovery.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 15, posted (7 years 6 months 3 hours ago) and read 3380 times:

Quoting SlamClick (Reply 14):
Sorry, never even heard about that event. (Guess I need to lurk in Civ/Av more )

TACA flight 110, in 1998. It flamed out because of a heavy downpour and the FAA got blamed for certifying an engine that you can't aim a firehose at, apparently.

I would have sworn that I heard about it from you! Damn your prolific hide, sir.

Quoting SlamClick (Reply 14):
I expect that cranes and barges might have been involved in the recovery.

Doesn't look like it. They changed an engine, fuelled it to the minimum, turned it around and flew it out of there like it was a repositioning flight.

Here's a link;

Taca 110 737 "Crash Landing" In New Orleans (by TriJetFan1 Nov 15 2004 in Civil Aviation)

Oh look - It was Gen_Av. Heh. And another;

http://aviation-safety.net/database/record.php?id=19880524-0



Todos mis dominós son totalmente pegajosos
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 16, posted (7 years 6 months 3 hours ago) and read 3373 times:

Quoting BAe146QT (Reply 15):
flew it out of there like it was a repositioning flight.

I did a quick google and saw one picture - looked like it was pretty well stuck in the mud.

Quoting BAe146QT (Reply 15):
the FAA got blamed for certifying an engine that you can't aim a firehose at, apparently.



Quoting BAe146QT (Reply 15):
They changed an engine,

Sounds like the FAA is also guilty of approving an engine you can't suck mud with!



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offline3DPlanes From United States of America, joined Apr 2006, 167 posts, RR: 0
Reply 17, posted (7 years 6 months 2 hours ago) and read 3361 times:

Quoting AirWillie6475 (Reply 5):
15c is standard temperature.

I should have been more clear... The charts are for standard, and for standard+15c. Same thing for my PHX example - I meant standard+35c, so 50c, not 35c.

Regardless, as SlamClick said, the charts used by the airlines just use the temp to work out the max weight - since the runway length is known.

But what about baro pressure? Since density alt comes from both temp and pressure (and humidity), where does the pressure come into the figuring?

It sounds like the charts I'm talking about (the "web of death" as Slam calls them) DO exist, just not at the individual pilot level - like in GA.



"Simplicate and add lightness." - Ed Heinemann
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 18, posted (7 years 6 months 2 hours ago) and read 3353 times:

Quoting 3DPlanes (Reply 17):
But what about baro pressure? Since density alt comes from both temp and pressure (and humidity), where does the pressure come into the figuring?

The airport analysis page is specific to the airport, which implies to the field elevation. They assume standard baro pressure and are okay to use unless the altimeter setting deviates (ie is less than) from standard by xx mb or more. This is usually to be found in the company (non-type-specific) operations manual. It takes a LOT of deviation to affect operations.

The pages I have at hand do not even have a baro correction table, where they do for antiskid inop or headwind/tailwind. These adjustments might be a weight change but more likely just a V1 adjustment.

The "climb limit" page is applicable to all runways.
Runway limits are each in their own column and slope & obstacle data is already figured.
Landing limits would be on a separate page.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 19, posted (7 years 6 months 1 hour ago) and read 3321 times:

Quoting 3DPlanes (Thread starter):
In my POH for a Warrior or 172, there are charts for calculating takeoff roll and required distance to clear a 50' obstacle.

Let me throw in a question here: If there is no obstacle at the end of the rwy, how long does it at least have to be ? The takeoff roll distance for a given aircraft, or the distance the aircraft needs in order to clear the (non-existant) 50ft obstacle ?



Exceptions confirm the rule.
User currently offlineKELPkid From United States of America, joined Nov 2005, 6343 posts, RR: 3
Reply 20, posted (7 years 6 months 1 hour ago) and read 3315 times:

Quoting A342 (Reply 19):
Let me throw in a question here: If there is no obstacle at the end of the rwy, how long does it at least have to be ? The takeoff roll distance for a given aircraft, or the distance the aircraft needs in order to clear the (non-existant) 50ft obstacle ?

Cessna gives you the numbers both ways, so you could use the "without" numbers.



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 21, posted (7 years 6 months ago) and read 3304 times:

Quoting KELPkid (Reply 20):
Cessna gives you the numbers both ways, so you could use the "without" numbers.

Ok, but is that permitted ?



Exceptions confirm the rule.
User currently offlineZeke From Hong Kong, joined Dec 2006, 8861 posts, RR: 75
Reply 22, posted (7 years 6 months ago) and read 3300 times:

Quoting CosmicCruiser (Reply 8):

we just input that info into the PAT onboard and it generates the data.

Is PAT like the BLT ? As that was the problem with both the accidents I listed.



We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
User currently offlineKELPkid From United States of America, joined Nov 2005, 6343 posts, RR: 3
Reply 23, posted (7 years 6 months ago) and read 3295 times:

Quoting A342 (Reply 21):
Ok, but is that permitted ?

For not-for-hire operations (part 91), single engine, the only thing that matters is that you get off of the ground safely. It's your call, as you're the one who will be calling the NTSB and/or FSDO to report the accident should it not work according to plan...there's no rule as to which takeoff/performance numbers you must use, although by law the manufacturer must provide them for your use  Smile A departure into the trees/power lines/rising terrain, in the absense of mechanical failure, will result in the NTSB determining the probable cause as "Inadequate preflight by the pilot in command."  Wink



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 24, posted (7 years 5 months 4 weeks 1 day ago) and read 3226 times:

Quoting KELPkid (Reply 23):
For not-for-hire operations (part 91), single engine, the only thing that matters is that you get off of the ground safely.

Just one more question: How about privately operated twins ? I guess, like on airliners, you could calculate the runway length needed for a safe single-engine takeoff after V1 (or what's the speed called at that you reach the "point of no return") ?

I'm sorry if I can't express it professionally !



Exceptions confirm the rule.
25 SlamClick : For the USA, we have FAR 91.13 that basically says that on one may operate an airplane (whether or not they intend to fly) in a manner as to endanger
26 CosmicCruiser : Sorry but I am not familiar with a BLT (short of the sandwich, LOL) but the PAT is the perf comp. on board. The only way it's wrong is if you input b
27 A342 : Ok, thanks for the answer.
28 OPNLguy : This incident occurred about 3 years after first deliveries of the 737-300s to various airlines, and investigation of this (and other) flameout incid
29 SlamClick : Okay, I do remember this issue: Known at my airline as "Madonna" cones (pointy) and "Dolly" cones (big, bulging rounded)
30 Post contains images KELPkid : You can compute an accellerate-stop distance, which provides the speed of "the point of no return" (i.e. you're commited to the takeoff after that sp
31 Zeke : BLT from what I understand is the Boeing Laptop Tool.
32 CosmicCruiser : Yea, that's what I guessed but curious how they gooned it up so bad. Were there no cross checks? Didn't some one say this doesn't look right? I can t
33 Zeke : Not 100% sure, have not seen the report, what I understand of the NZ SQ incident was they were out by 100t on ZFW, TOW was then also out be 100t. The
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