required runway length
 

It has long been the 'mantra' within the industry that "if you don't have 3,000m, forget it." (for B747Fs anyway)

What do airlines/pilots assume to be the minimum requirements for B733, B752, B762, B747?

Appreciate that this is a broad topic however, looking at what boeing indicate on their website, airlines/pilots must make a further % reduction on the recommended take-off requirements.

e.g. B752, standard day, can take off at approx. 93% MTOW on 2,000m sea level flat runway.

Would any airline/pilot operate by these parameters and what allowance is there for pay load and range restrictions?

Operated B742 into/out 2328m on RPT, Req'd ALL stopping stuff to be servicable, and a "positive" landing technique. In addition we had the capability to Op into/out 1936m with some heavy Perf limitations.

Santos Dumont -Rio de Janeiro - has,if I'm not mistaken a Rwy length of 1300 m.Used regulary by a lotof planes ,737,A320,etc.

As a starting point, I drew up this table (incorporating the data posted above). If anyone has better figures or refinements, then please post them and we can refine this a bit more. Normal word of warning - a/c performance is a sophisticated computation so don't use this table for real!

EDITED - THIS TABLE SUPERSEDED - SEE REVISED TABLE IN LATER POST

I hate it when i write things on a scrap of paper and then cant decipher it...... :(

Anyway for the extreme values which work for the whole temperature envelope.

747-400 = 2133m T/O Wt = 340k
747-200 = 2072m T/O Wt = 312k
757-200 = 990m T/O Wt = 71.5k
777-200 = 1550m T/O Wt = 200k

I didnt have a chance to check the empty weight of a B757, however the others are giving quite a payload. Most appear to be VMCG limited.



Mutt.

I've added in Mutt's figures and updated the table which is shown below. Mutt's figures for the 747-400 equate to a 747-400ER, 340 tonnes, ISA +17 deg C, PW4062 engines, sea-level airport. For 2133m runway, that allows 220,000 kgs OEW + payload. That means up to 370 pax @ 96 kg/pax (after making some assumptions about empty weight). That’s good for about 5200 NM range in nil wind incl. reserves. Factor in the commercial reliability factors of 85% winds on an west-east-west routing, and a bit of extra holding, and it brings the dependable range down to about 4,200 NM. The revised table is now:
Notes
757-200 TOW 71.5k
737-400 sealevel runway, ISA +15 degC at takeoff, 22,000 lb CFM engines, 100 pax, 1000NM commercial range
777-200 TOW 200k
747-200 TOW 312k
747-400ER TOW 340k, sealevel, ISA +17 degC, PW4062, 370 pax, 4200NM commercial range

Thanks for the information guys, it's very useful.

Mutt/OverRun, I note with interest your figures for B744ER. From your table OverRun, is it safe to assume that operators will base any decision on the 'Normal' rating characteristics? i.e. 3,100m for B742 ops.

Thanks again!

If any operator or airport based any decision on the 'Normal' rating characteristics i.e. 3,100m for B742 ops, I'd be the first to kick their arse from here to breakfast time.

They, or their performance engineers, would be analysing the route, checking distances, takeoff obstacle limitations, temperatures at takeoff and en-route, winds en-route weather, fuel loads, alternates, holding fuel, cargo, onboard spares, OEW for their particular aircraft, and pax loadings, as well as runway length, gradient, surface, and wind statistics. Then if they got an answer somewhere near 3100m, they might mutter that 'overrun's table is the living proof of how the dumb can occasionally luck out with the numbers'. Air France 747-200s might use 3100m out of CDG except when they return from Johannesburg using 3600m or when they fly to TelAviv using 2600m or fly out of St Maartens using 2072m
http://www.airliners.net/open.file/201517/M/

OverRun has summed it up quite nicely, each airport is specifically assessed, we dont have any fixed rule stating that we will not operate the B747-200 into runways less than 2100m.

In fact we operate into Rome and Paris where the runways are close to 2100m without any complaints. The runway which causes the most complaints is 3100m without any obstacles, the takeoff weight is limited by the accelerate stop, we operate 10 hour sectors from there at the maximum weight. The runway end and those red lights appear quite close as you run out of tarmac.

Mutt.

I appreciate the comments.

I understand that an operator or airport takes many factors into consideration however, if the operator is to BASE an aircraft from a particular airport which may be required to work on a number of different routes/payloads, will their assessment of the runway requirements not have to take the most conservative assumptions?

Conservative Factors
 

In those situations where I have been involved in analysing performance, weve taken a more pessimistic view. We created a flow chart of likely scenarios which could involve the requirement for extra runway length, the type of pavement (whether grooved or ungrooved or gravel etc.), runway width and runway conditions.

Safety of the aircraft and its occupants is our primary concern and we look at the probability of an event that might increase the take off and stopping distances.

For example, an aircraft reaching V1 that suffers a double engine failure on take off due to say a bird strike, may have limited braking capability from lack of reverse thrust and reduced hydraulic and accumulator braking pressure. A double engine failure is a rare event but this scenario was played out by a Boeing 707 in Sydney in the early 1970s and the aircraft overan the runway departure point. In areas where there is a high bird population, the safety margins are siginifcantly reduced.

In the Qantas Bangkok accident (VH-OJH), we summised that the aircraft could have stopped safely had reverse thrust been available. However, brakes are the primary equipment for stopping the aircraft. In that accident, the descent rate of the airplane remained unchecked and touch down occured "inadvertantly" resulting in ground spoiler deployment. If the decison to continue with a go around had been maintained at that point the aircraft would still have been on the ground at the departure end of the runway in ground effect at twice the speed.

Pilots need to exercise extreme care that they plan an exit strategy based on more than just engine failure.

Good performance planning involves looking at different scenarios and making sure you do not plan for a disaster.

What if this happens should be followed by a serious appraisal - it's not a joking matter. This requires intimate knowledge of aircraft performance.

Working a fully serviceable aircraft of a minimal strip length in ideal conditions can result in complacency.


:suspect:

generallee,

We are doing that right now, we are seeking a new type of fleet aircraft for a particular route structure. The manufacturers will tell you that the aircraft has no problem taking full payload on the selected route provided it departs to the north, they omit to tell you that you will leave passengers behind if you depart to the south.

So we will err on the conservative side and base assumptions on the less than optimum runway and a pretty hot temperature.

However, even on a 4 engine aircraft we wont base decisions on a double engine failure.

Mutt.

(how did you make that table format ?)

Two things,
1: Maersk Air services EKVG on 1250 m with 737-3/500 (and I think I've seen a -400 there once or twice)

2: 990 m for a 572... has that actually been done or is it pure paperwork ?

Purely theoretical, its the minimum length were we can comply with all takeoff requirements, however as we only have 1 B757 VIP aircraft we have never had to use such a runway.


Mutt.

But can you land it legally on 990 meters ? The T/O I could be made to believe, but landing legally on 990 meters.... I'll need some coaxing to believe that.

Guess that it depends on if you plan to land there using the 60% rule or divert there during flight. :)

Sorry, dont have books or computer on hand to give you a proper answer.

Mutt.

Yup! It is all down to specifics but I have just had the chore of looking at a 737-800. So you are all going to suffer.

It is accepted that the take-off performance of an aircraft is directly proportional to the square of its weight and inversely proportional to the product of air density, wing area, lift coefficient and effective thrust.

I now refer you to the following URL on the official Boeing site:

http://www.boeing.com/assocproducts/...s/737wsec3.pdf

which is Fig 3.3.36 JAR Take-off Runway Length Reqmts. For a temperature of 30deg C and a wet smooth surface the performance of the B737-800 with CFM56-7B27B1 engines at 27,300lb static thrust is tabulated. At this point I must stress that in practice either or both the Boeing Laptop Tool and the on-board Flight Management Computer Systems are used to calculate exact settings. The generalised corrections implicit in paper tables err on the conservative side by as much as 5 tonnes and maybe double that on the 777.

I now refer you to the Quick Reference Handbook (QRH) for that very same bobby 737 aircraft and extract the following sea-level table.

Weight Weight V1 VR V2
tonnes Lbs kts kts kts
65 143325 140 144 150
60 132300 134 138 145
55 121275 128 130 140
50 110250 122 124 135
45 99225 115 117 130
40 88200 108 110 125

Back to school and develop from these parameters the implicit stall characteristics and lift coefficients eg an XL spreadsheet helps.

I have adopted here a particular day when barometric pressure and relative humidity are such that the airfield density altitude is 2000ft. There is now sufficient data to hand, albeit with generalised rather than specific corrections to predict take-off lengths and correlate them with the Boeing paper graphs using line regression techniques. A simpler analysis whereby JAR Length = 16.5(W^2/ Density ratio x Sw x CLmax x [email protected]) + 500 provides almost indistinguishable results, specifically of course for the 737-800 and no other.

If you want a 744 or a 772 analysis (groan) I can do it but my figures will always underestimate the computer in weight capacity by anything from 3-7%.

Anyway notwithstanding all these gripes if I were a pilot in a B737-800 on the runway at FACT with Outside Air Temperature 30o C, Dew Point 15o C and barometric pressure 1017mb the JAR take-off length for 145,000lb gross weight would be 5995ft. Allowing 92,000lb weight for the aircraft operationally ready but empty and 115,000 for the zero fuel weight this would accommodate 100 passengers. My own spreadsheet tabulations are now shown.

Weight W2/sSw CLmaxT JAR Length
lbs Feet
145000 333 5995
140000 309 5599
135000 286 5219
130000 264 4856
125000 243 4510
120000 223 4180
115000 204 3866
110000 185 3553
105000 168 3272
100000 152 3008
95000 137 2761


I now refer you to the following site:

http://www.boeing.com/assocproducts/...s/737wsec3.pdf

and specifically Figure 3.2.2 which is a Payload/Range tabulation. You will see that subject to the alternate diversion, fuel reserves and flight profiles mentioned that the aircraft has a range of 2000 nautical miles. This is an extra margin of 300 nautical miles over my intended flight showing just how coarse paper charts with their generalised conditions can be.

What you really do of course is use the electronic hardware fitted and authorised but if your responsibility stops, so do the bucks in the paycheck and you have the honour to be first at the scene of the accident. So you do have to know how to use first principles to test and see if a localised issue makes sense.

Sorry if this is dreadfully long but as the enicalyth was just in the middle of having its patience tried by a complete drongo I am offering the paperwork with the expletives deleted. Now let me get out from behind this desk and go fly something, a kite even!
Once the whole shebang is certified, rubber stamped and the cat's mother has pee'd all over it I write the SOPs and you, Lucky Jim, do what the book says. So how long was that runway? Gawd, they've all nodded off!

enicalyth


Welcome to Tech Log..... I'm glad that I read your message in the morning..:):)


Mutt.