FedEx MD-11 crash at Narita

[flyboy2548m]

A question to all pilots and aviation experts here (and I am not discarding your answer Flyboy, just curious):

Do you correct this MTOW according to the altitude above sea level and lenght of the takeoff runway? Or do you only mind about the rotation speed?

In other words: do you have a MTOW for different runways? (According to lenght and altitude above sea level?)

Yes, we absolutely do correct it. This is why it is my job for every flight to calculate the following five weights:

1. Structural MTOW (that's that 630,500lbs number in case of the MD-11). This one can be lower than the certified number for certain MEL/CDL items

2. Runway-limit weight (that comes right from the dispatch release and is density altitude-dependent, but, oddly enough, in case of the CRJ it's almost always higher than the structural MTOW.)

3. Climb-limiting weight (ditto)

4. Burn-limiting weight (MLW+fuel burn, this is usually the lowest number and is our most restrictive number).

5. ZFW-limiting weight (MZFW+fuel on board, usually the second-most restrictive number).

[Putt4Par]

[quote="flyboy2548m
Yes, we absolutely do correct it. This is why it is my job for every flight to calculate the following five weights:

[/quote]


Just out of curiousity...

For your calculations and based on your airline's guidelines, what weight number do you assign for each passanger? Does that number include
luggage or do you calculate luggage based on actual numbers from the ramp?

[flyboy2548m]

Just out of curiosity...

For your calculations and based on your airline's guidelines, what weight number do you assign for each passenger? Does that number include
luggage or do you calculate luggage based on actual numbers from the ramp?

Pax are 184 per in the summer and 189 per in the winter. Baggage is the actual number from the ramp or load control.

[Putt4Par]

Just out of curiosity...

For your calculations and based on your airline's guidelines, what weight number do you assign for each passenger? Does that number include
luggage or do you calculate luggage based on actual numbers from the ramp?

Pax are 184 per in the summer and 189 per in the winter. Baggage is the actual number from the ramp or load control.

That seems fairly light when you consider the amount of fat asses we have in America. At the same time, many kids and women under 184lbs travel too so
I guess that makes up for that.

[Half Bottle]

Just out of curiosity...

For your calculations and based on your airline's guidelines, what weight number do you assign for each passenger? Does that number include
luggage or do you calculate luggage based on actual numbers from the ramp?

Pax are 184 per in the summer and 189 per in the winter. Baggage is the actual number from the ramp or load control.

That seems fairly light when you consider the amount of fat asses we have in America. At the same time, many kids and women under 184lbs travel too so
I guess that makes up for that.

Don't forget it includes the weight of their clothes, coats and any carry-on baggage, too. Sometimes my briefcase weighs as much as a small child.

[3WE]

Yes, I didn't expound enough.

"The Zero Fuel Weight (ZFW) of an airplane is the total weight of the airplane and all its contents, minus the total weight of the fuel on board.

For example, if an airplane is flying at a weight of 5,000 lb and the weight of fuel on board is 500 lb, the Zero Fuel Weight is 4,500 lb. Some time later, after 100 lb of fuel has been consumed by the engines, the total weight of the airplane is 4,900 lb and the weight of fuel is 400 lb. The Zero Fuel Weight is still 4,500 lb.

Note that, as a flight progresses and fuel is consumed, the total weight of the airplane reduces, but the Zero Fuel Weight remains constant (unless some part of the load, such as parachutists or stores, is jettisoned in flight).

For many types of airplane, the airworthiness limitations include a Maximum Zero Fuel Weight."

Some aircraft do not have a published MZFW. All powered aircraft require fuel, therefore the weight of the aircraft minus fuel is the ZFW.

When an airplane is being loaded with crew, passengers, baggage and freight the total weight must not exceed the aircraft's published Zero Fuel Weight.

When an airplane is being loaded with fuel it must not maximum permissible takeoff weight. The planned fuel burn must place the aircraft at or below the max landing weight.

MZFW : The maximum weight of an aircraft prior to fuel being loaded.

ZFW + FOB = TOW

For any aircraft with a defined Maximum Zero Fuel Weight, the maximum payload can be calculated as the MZFW minus the OEW (Operational Empty Weight)

MaxPayload = MZFW − OEW.

Are you Gabriel?

Yes, I didn't expound enough.

Are you 3WE?

[RadarContactLost]

BTW, the current MTOW of the MD-11 is 630,500lb.

A question to all pilots and aviation experts here (and I am not discarding your answer Flyboy, just curious):

Do you correct this MTOW according to the altitude above sea level and lenght of the takeoff runway? Or do you only mind about the rotation speed?

In other words: do you have a MTOW for different runways? (According to lenght and altitude above sea level?)

Yes, it's done for every airline flight by a 121 carrier. You have the max structural weight which is the number you recite for a checkride oral but performance numbers are calculated for every takeoff. You work backwards from the landing weight limit at your destination plus the planned fuel burn. And you need to check that the landing weight is OK at your alternate if you have one on the release. Then you have to see if you can make the V1 cut and either stop or get to 35 feet in the distance available. You account for the airport elevation, the pressure altitude, density altitude, the runway slope and any headwind or tailwind. Then you have to see if you meet the climb gradient, second segment is almost always the hardest to meet with one engine inop and the flaps set for TO. This also varies with temperature. And if there are any obstacles off the end of the runway, you'll have to back everything up. So you can be structurally limited, landing weight limited, runway limited, climb limited, or obstacle limited. And some planes require you to figure the max brake energy and that may affect your takeoff weight. Then you have to see if any MEL/CDL items change your numbers.


Some evening I've waited for the next hour's weather report to see if it would change our allowable weight.

[VectorForFood]

Many airlines when factoring Weight & Balance of checked baggage factor 25 pounds per each checked bag.

As any ramp agent will tell you, that is a crock of sh!t.

[Peminu]

Thanks Flyboy and Radar CL for your answers.

Now I see another big issue for delaying a flight.

[Schorsch]

Just out of curiosity...

For your calculations and based on your airline's guidelines, what weight number do you assign for each passenger? Does that number include
luggage or do you calculate luggage based on actual numbers from the ramp?

Pax are 184 per in the summer and 189 per in the winter. Baggage is the actual number from the ramp or load control.

That seems fairly light when you consider the amount of fat asses we have in America. At the same time, many kids and women under 184lbs travel too so
I guess that makes up for that.

The number is a guess and especially does not account for North American travellers.
An average A380 passenger weights 101.8kg including luggage, that is design directive.
Flyboy's CRJ has some reserves in case thew people are preposterously fat, just do not take the short runway!
The actual Gross weight of an aircraft has a margin of error of 1% and more, means that a B747-400 can have 4t difference between assumed gross weight and actual gross weight.

[Schorsch]

BTW, the current MTOW of the MD-11 is 630,500lb.

A question to all pilots and aviation experts here (and I am not discarding your answer Flyboy, just curious):

Do you correct this MTOW according to the altitude above sea level and lenght of the takeoff runway? Or do you only mind about the rotation speed?

In other words: do you have a MTOW for different runways? (According to lenght and altitude above sea level?)

Actually, MTOW is quite a random number.
Many boundaries may define it, like performance or structural loads. Performance limits normally assume a less than optimal airport (temp above ISA, no headwind). But that does not account for all conditions. See recent doubts by Mexican about B787 performance promises.

[andrasz]

Actually, MTOW is quite a random number.

To elaborate a bit further, certified MTOW may be quite different to design MTOW. As ATC and airport charges are typically a function of MTOW, many airlines who do not need the maximum range of a particular type elect to reduce the certified MTOW to save on charges. In practice this means that even if the aircraft is designed to a higher MTOW, the legal limit is lower. While this is more common for short range a/c, I have heard of some airlines playing around with the MTOW of the longhaul fleet too.

[flyboy2548m]

Actually, MTOW is quite a random number.

To elaborate a bit further, certified MTOW may be quite different to design MTOW. As ATC and airport charges are typically a function of MTOW, many airlines who do not need the maximum range of a particular type elect to reduce the certified MTOW to save on charges. In practice this means that even if the aircraft is designed to a higher MTOW, the legal limit is lower. While this is more common for short range a/c, I have heard of some airlines playing around with the MTOW of the longhaul fleet too.

The CRJ100/200 is a very good example of that. Originally the marketed MTOW was 51,000lbs. That's since increased to 53,000lbs.

[Procede]

Actually, MTOW is quite a random number.

Isn't there a structural MTOW, based on the maximum weight the landing gear is designed to hold? Everything else is dependant on temperature and air density, but there is a 'do not exceed' weight.

I've always understood that the MZFW is a function of the wing root bending moment. As such everything in the fuselage, including the contents of center and belly fuel tanks are included in this number and only the fuel in the wing is excluded.

To elaborate a bit further, certified MTOW may be quite different to design MTOW. As ATC and airport charges are typically a function of MTOW, many airlines who do not need the maximum range of a particular type elect to reduce the certified MTOW to save on charges. In practice this means that even if the aircraft is designed to a higher MTOW, the legal limit is lower. While this is more common for short range a/c, I have heard of some airlines playing around with the MTOW of the longhaul fleet too.

Won't most airports have a fixed charge for a given aircraft type, based on the MTOW of that (sub)type? So you might have a difference between a 747-400 and 747-400ER, but not between different engine types, airlines, etc.

[flyboy2548m]

Isn't there a structural MTOW, based on the maximum weight the landing gear is designed to hold?

There is, but that number may be well above what the manufacturer is willing to certify the aircraft at. The "physical" MTOW for the CRJ may be 60,000lbs, for all I know, but Bombardier is presently comfortable with 53,000lbs.

[Cam]

Many airlines when factoring Weight & Balance of checked baggage factor 25 pounds per each checked bag.

As any ramp agent will tell you, that is a crock of sh!t.

I know WJ puts a HEAVY tag on bags over 40 lbs. But the load control sheets from YYC have an average for the weight of bags and cargo. If all bags were 25lbs I'd be happy...

[Schorsch]

There are hard limits for MTOW, but they are rarely exploited.
Structural limitations may be static loads (for example the classic 2.5g vertical maneuver), but may also come from fatigue loads assessment.
A twin-jet can - if we assume friendly airfield conditions - always lift 10-20% more than actually given, but it may exceed some structural loads in some part of the flight envelope. That doesn't mean the aircraft breaks up shortly after take-off, the design limit loads are kind of theoretical (2.5G vertical maneuver with .97*MTOW at MMO&VMO). And overbuilt aircraft like the CRJ will be hard to destroy.

[andrasz]

A twin-jet can - if we assume friendly airfield conditions - always lift 10-20% more than actually given, but it may exceed some structural loads in some part of the flight envelope. That doesn't mean the aircraft breaks up shortly after take-off, the design limit loads are kind of theoretical (2.5G vertical maneuver with .97*MTOW at MMO&VMO). And overbuilt aircraft like the CRJ will be hard to destroy.

The design standards of all western-built commercial aircraft call for the design strength of each individual part be 35% higher than the maximum structural load bearing down on that part. As maximum design structural loads are typically 15-20% above certified maximums, this gives a roughly 50% margin over certified maximum loads before any component will fail (in theory).

Because the Russians had less faith in the quality and consistency of their metallurgy, their designs had a 50% above designed structural loads requirement for each part, which explains why all russian aircraft are significantly heavier (but stronger) than their similar capacity western counterparts. The Sukhoi SSJ is the first russian aircraft to be manufactured to the lower 35% limit.

[andrasz]

Actually, MTOW is quite a random number.

Won't most airports have a fixed charge for a given aircraft type, based on the MTOW of that (sub)type? So you might have a difference between a 747-400 and 747-400ER, but not between different engine types, airlines, etc.

No. Most airports charge by the MTOW formula (and all ATC providers do) that is either calculated for individual tail numbers, or more commonly (Eurocontrol, most major EU airports) for the average of a given airline's fleet. Typically the weights are averaged per IATA aircraft type code, so if the ER has a separate code (eg. 773/77W) then the charges will be different, if not (eg. 763) then the charge will be the same (giving an unfair advantage to an airline that has a mix of standard and ER 767-300s, but life is not fair, is it ... ?)

[3WE]

Great discussion of MTOW and related factors. So, while we'll need to wait for the final report, I assume this means there's parlor consensus that errors in the average suitcase and passenger weight caused the MD-11 to be over weight and run off the end of the runway while trying to take off....

[GlennAB1]

http://www.yomiuri.co.jp/dy/national/20 ... Y03103.htm

The FedEx Corp. cargo plane that crashed on landing at Narita Airport on March 23 was not equipped with a warning system that can predict wind shear, or sudden and violent changes in wind direction, according to a Construction and Transport Ministry investigation............
The FedEx plane was notified by airport traffic controllers of wind shear and strong winds near ground level, at four minutes before landing, then at two minutes.

---------------------------------------

Note: The A/C has EGPWS

[flyboy2548m]

http://www.yomiuri.co.jp/dy/national/20 ... Y03103.htm

The FedEx Corp. cargo plane that crashed on landing at Narita Airport on March 23 was not equipped with a warning system that can predict wind shear, or sudden and violent changes in wind direction, according to a Construction and Transport Ministry investigation............
The FedEx plane was notified by airport traffic controllers of wind shear and strong winds near ground level, at four minutes before landing, then at two minutes.

---------------------------------------

Note: The A/C has EGPWS

Glenn,

I was under the impression that you were an avionics tech at FedEx. How do you not know that all of their MD-11s are equipped with a windshear warning system that's actually part of the radar and that it operates from 1,500 AGL down?

[GlennAB1]

http://www.yomiuri.co.jp/dy/national/20 ... Y03103.htm

The FedEx Corp. cargo plane that crashed on landing at Narita Airport on March 23 was not equipped with a warning system that can predict wind shear, or sudden and violent changes in wind direction, according to a Construction and Transport Ministry investigation............
The FedEx plane was notified by airport traffic controllers of wind shear and strong winds near ground level, at four minutes before landing, then at two minutes.

---------------------------------------

Note: The A/C has EGPWS

Glenn,

I was under the impression that you were an avionics tech at FedEx. How do you not know that all of their MD-11s are equipped with a windshear warning system that's actually part of the radar and that it operates from 1,500 AGL down?

You have me confused with someone else.

Yomiuri is correct.......

There is a thing called "Effectivity," not All are.......

[AndyToop]

I've always understood that the MZFW is a function of the wing root bending moment. As such everything in the fuselage, including the contents of center and belly fuel tanks are included in this number and only the fuel in the wing is excluded.

I thought usable fuel in the center tanks is excluded from ZFW, provided it is to be burned before the (or at least the vast majority of the) fuel in the wings.

I vaguely recolect something about some types needing to include fuel in the certain tanks in the ZFW, but I thought these were the exception rather than the rule.

[Dmmoore]

The FedEx MD-11 fleet has a wind shear detection system installed. The system does not predict, it detects and notifies the crew of a wind shear when the aircraft encounters one. The predictive wind shear system is being installed but it will take 2 years to complete the installation on the fleet.