Max quick turnaround weight definition

[JammedStab]

Would be interested to know what the exact definition is and any real world scenarios where it applies.

Thanks

[alatriste]

Qick turn around limitation could be considered on those airplanes without brake temperature indication,
If landing conditions leads to high GS on short runways, next OTOW might be limited by brake energy if a minimum turn around time is not spent and OAT is higher than a critical point upon landing.
for MD 80 series a minimum time of 25 minutes is considered.
Example.
LEMD, 2000 elevation, OAT 40C, critical temperature 19C, 10kt tailwind, 10000 TORA.
next takeoff weight will be reduce in 4200 lbs cause of this restriction if turn around is less than 25 minutes (almost impossible to make it).
Regards.

[Skyjob]

The Maximum Quick Turnaround Weight definition is the weight at which after waiting for the maximum amount of time allowable in accordance to your AFM (for the type and brake category fitted to the airplane involved) the fuse melt WILL NOT occur or have occurred.
Different times exist as per configuration and can be found in tabular form in your AFM.
For example 737NG AFM refers to 48-67 minutes depending on type of brakes and model.

For all brake categories: After landing at weights exceeding those determined from the maximum quick turnaround option in AFM- DPI, wait at least the Minimum Wait Time indicated in the table below and check that wheel thermal plugs have not melted before making a subsequent takeoff.

Real world scenarios do not generally use this data as this would mean the aircraft would have to wait for this specified minimum time before commencing onto another flight departure. Most airlines do not want to be restricted by this ground time, e.g. a ULCC using 25 minutes has little to gain applying the MQTW rules.

Instead, Recommended Brake Cooling charts exist for those landings which are not limiting but need thus evaluation of potential reduced cooling time requirements (less then time in accordance with AFM). Always observe these limitations and release brakes in accordance with operating procedures for the time specified according to these charts.

[wiggy]

any real world scenarios where it applies.

What alatriste said:

Qick turn around limitation could be considered on those airplanes without brake temperature indication,

Comes into play on the 777 if the brake temperature indication system in inop.

[BOAC]

JS -you will find this thread of use.

Out of interest, I do not recall the 'limit' ever being notified to me in 3 companies (737). I could never see any point in it either, since it relates to max breaking, no reverse and I don't think it accounts for taxi distance which is additive.

[theXfactor]

Depends on how your performance limits are computed.
Back in the day, the 727 had a 55 min turn limit until we had to refer to the charts for brake cooling. (Did not have brake temp gauges)
It was mainly due to brake cooling for a rejected T/O.

Everything I have flown since, my min turn was 8 hrs.

But seriously...My understanding is that stuff with brake heat monitoring, is that if it is in the green , you are good to go.

[Frequent Traveller]

Quick Turnaround vs brakes cooling ?

TwinAisleFeeders has developed a "Quick Rotation" feeder concept with twin aisle narrowbody cabins reconfigured 1+3+1 (vs 3+3 today) applicable to A32X Series (---> H2XQR), 73X Series (---> H3XQR) and/or 75X Series (---> H5XQR) where the idea is to reduce ground rotations sufficiently to impact upon the trip cost picture and restore economic balance through extra freight and/or Product Differentiation ... we have explored possible interferences from "Brakes Cooling System Inop" making the concept not workable but have found in-service statistics show good-to-very-good dependability upon BCS ... in certain climatic zones/specially exposed airfields though, shortening ground rotations (by eg - 16.5 minutes for H21QR vs A321 at high loadfactors) could require intervention of a service vehicle offering chilled air Landing Gear cooling externally ? Do you Gentlemen think such a solution would be of proper assistance to keeping brakes temperatures within maxima

[Skyjob]

At many weights when REVERSERS are used properly there is no requirement for any cooling if you want to achieve minimum turnaround time.

For example on B738, 60T (representing a 43T ZFW, 2T fuel + 15T payload = >160 pax with a bag each!), calm winds, ISA day, DRY runway (no credit for reverse thrust in LDR taken):

Autobrake 2, idle reverse: Vref30 = 147 kts, Vat = 152 kts, Vbrakes = 149 kts => cooling 41 minutes, LDR = 2233m
Autobrake 3, idle reverse: Vref30 = 147 kts, Vat = 152 kts, Vbrakes = 149 kts => cooling 49 minutes, LDR = 1724m
Autobrake 2, idle reverse: Vref40 = 139 kts, Vat = 144 kts, Vbrakes = 141 kts => cooling 30 minutes, LDR = 2037m
Autobrake 3, idle reverse: Vref40 = 139 kts, Vat = 144 kts, Vbrakes = 141 kts => cooling 40 minutes, LDR = 1578m
Autobrake 2, 2nd detent reverse: Vref30 = 147 kts, Vat = 152 kts, Vbrakes = 149 kts => cooling 0 minutes, LDR = 2233m
Autobrake 3, 2nd detent reverse: Vref30 = 147 kts, Vat = 152 kts, Vbrakes = 149 kts => cooling 16 minutes, LDR = 1724m
Autobrake 2, 2nd detent reverse: Vref40 = 139 kts, Vat = 144 kts, Vbrakes = 141 kts => cooling 0 minutes, LDR = 2037m
Autobrake 3, 2nd detent reverse: Vref40 = 139 kts, Vat = 144 kts, Vbrakes = 141 kts => cooling 10 minutes, LDR = 1578m

In other words if you fly slower (flap 40 vs 30), brake less (auto brake 2 vs 3), use reversers properly and provided LDA is sufficient then it is possible to achieve those times.

[Frequent Traveller]

Thanks Skyjob ... we want to put real pressure on things turning around ! We are carrying the Banner for a "Groundworthiness Certificate" to spell out a normative for ground operations. There's two levels : Block Time and Gate Time (or Slot Time), the last one from "Fasten Seat-Belts" sign off flight N-1 till push-back flight N, but the total ground time is really from touch-down till lift-off. But possibly you Flight Deck people count the apron taxi-time (and airport control Tower/ATC-induced queuing, plus LDR and TOR as well) into what you refer to as the "flight time" ? Would this viewpoint change with speed Towing (whether electric or Diesel-powered ...) ?

[Skyjob]

Frequent Flyer, I am not sure what your background is, but certain defined times are as per Air Ops and thus cannot be amended. These times will not change with the introduction of a towing. Some variations exist to certain definitions between operators to keep some bean counter in a far away located office happy, but generally...

Different flight segments are labelled differently for different obvious reasons:

• Flight Time - Takeoff (advancing thrust levers to takeoff position) to landing (by selection of idle reverse after reverse use requirements)
• Block Time - the time between blocks off to blocks on, the prior can vary between airlines (moving under its own power, or commencement of pushback, or engine start for the purpose of departure) but the latter is generally defined as engines shut down, parking brake set, "belts off",...)
• Gate Time - the time spent at the gate (this is the physical time located at the gate, so equal to you "belts off" to closing doors for departure)
• Slot Time - equivalent to a controlled time of takeoff (CTOT), thus should not be used in your definition as something else as it would be too confusing for operators to refer to something using a term they are already used to in a different manner
• Ground Time is generally not used as a definition but can be used as time between flights.

Hope this helps, PM to avoid continuation on the MQTW thread...