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Commercial Airplane Operators
Commercial Airplane Op  
QUESTION: Dear Norkus

1. Is the Cargo carrying capacity (Load, Weight) fixed or standard in all Commercial Airplane Carriers ?. Is this done for Security measure for not exceeding the total weight, load of the airplane i.e passengers, cargo, fuels, airplane etc ?  

2. Is there a certain Total Load or Weight of the Airplane which cannot be exceeded ?. Is this identified by Electronic Instruments panel, Alarms etc indicating the Total Weight, Load of the Airplane to the pilot before flight takes off ?.

3. In case if the Total Load or Weight of a Airplane is exceeded
and still the Pilot tries a take off, can it lead to plane crash ?

Awaiting your reply,

Thanks & Regards,
Prashant S Akerkar

ANSWER: 1.) Is the Cargo carrying capacity fixed or standard in all Commercial Airplane Carriers?

No, not at all. It varies greatly depending on the aircraft. In addition performance or structural factors affecting a flight can further reduce the maximum weight limits on any given flight.

1a.) Is this done for Security measure for not exceeding the total weight?  
Aircraft specific weight limitations have nothing to do with "security measures". Perhaps you mean safety measures? If so, then yes, such weight limits are supposed to keep the aircraft within a safe operating envelope.

2.) Is there a certain Total Load or Weight of the Airplane which cannot be exceeded ?

Absolutely.

Maximum takeoff weight/MTOW is the maximum weight at which the pilot of the aircraft is allowed to attempt to take off, due to structural or other limits. "Other" may be performance related. "Structural" limitations might prohibit an aircraft from departing with a full fuel load and/or full passenger or cargo restrictions. On short flights it is often the case an aircraft cannot be loaded to capacity because the fuel burn off enroute will not be sufficient to allow the aircraft top land at or below the Maximum Landing Weight/MLW.  Maximum landing weight is the maximum aircraft gross weight due to design or operational limitations at which an aircraft is permitted to land.

http://en.wikipedia.org/wiki/Aircraft_gross_weight

Each aircraft also has specific limits on the weight of cargo per cargo hold that may be carried, weight of fuel per tank, and passenger capacity.   

2a.) Is this identified by Electronic Instruments panel, alarms etc indicating the Total Weight, Load of the Airplane to the pilot before flight takes off?

It is not identified on any "instrument". The maximum taxi and takeoff weights are calculated by the crew or via an airlines dispatch for the crew. The weights are based on "standard" weights per passenger and per bag. This is usually averaged at about 190lbs/87kg per passenger or 30/lb/14kg per bag depending on the airline. Weights are also increased a bit during the winter months. The exact weight is not known unless the actual weight of each passenger and their luggage is used.

If an aircraft is equipped with a Flight Management System/FMS computer the passenger, cargo and fuel weight can be entered into it. This will provide the crew with their "actual" weight throughout the flight based on initial figures. This is another way to check that the landing weight of the aircraft is within limits and if the fuel used matches the planned fuel burn enroute and for landing.

3. In case if the Total Load or Weight of a Airplane is exceeded and still the Pilot tries a take off, can it lead to plane crash?

It most definitely could and has. Several fatal accidents that have been attributed aircraft exceeding weight limits. Here is a listing of events where crashes were caused due to weight factors-

http://aviation-safety.net/database/dblist.php?Event=CGO

Hope this helps.


---------- FOLLOW-UP ----------

QUESTION: Dear Norkus

Thank you.

Can this be considered as a part of Airplane Load / Stress Testing methods ?.

Can we derive some mathematical formula or equation to calculate / compute the Total Weight of the Machine (Airplane) before takeoff ?

Parameters : temperature, maximum power of the engines etc

1 Ton = 1000 kg

Example :

1. Aircraft Weight : x kg - Construction (Manufacturing)
2. Fuels Weight : y kg - Construction (Manufacturing)
3. Passengers Weight : z kg - Load - Includes Crew Cabin - Pilot, CoPilot, Captain etc - Load
4. Cargo Weight : - n kg - Load
5. Miscellaneous Weight - Furniture - Seats, Tables, Utensils - Dishes,Glasses etc) - m kg - Load

Total Weight of the Aircraft W in Tons = x + y + z + n + m.

Should we add safety factor value to this total weight ?

Do you feel electronic instrument panels calculating and showing the Total
Weight (Load) of the aircraft can be useful for Pilot before he takes a take off ?. Alarms will buzz to the Cabin Crew if Overload occurs within the aircraft before the Take Off.

Among different accidents, which are the most likely to occur because of Aircraft Overweight ?

1. During Takeoff.
2. During Landing.
3. During Aircraft flight (i.e. After Plane Takeoff and Before landing).

Awaiting your reply,

Thanks & Regards,
Prashant S Akerkar

Answer
1) Can this be considered as a part of Airplane Load / Stress Testing methods?

I have no engineering background and do not know what the manufacturer does to determine weight limits, but stress testing is only part of it. However, guidance from the Federal Aviation Administration is provided here under Federal Aviation Regulation Part 25: Airworthiness standards: Transport category airplanes-

This is just one of many:
Sec. 25.25 — Weight limits states:
(a) Maximum weights. Maximum weights corresponding to the airplane operating conditions (such as ramp, ground or water taxi, takeoff, en route, and landing), environmental conditions (such as altitude and temperature), and loading conditions (such as zero fuel weight, center of gravity position and weight distribution) must be established so that they are not more than—

(1) The highest weight selected by the applicant for the particular conditions; or

(2) The highest weight at which compliance with each applicable structural loading and flight requirement is shown, except that for airplanes equipped with standby power rocket engines the maximum weight must not be more than the highest weight established in accordance with appendix E of this part; or

(3) The highest weight at which compliance is shown with the certification requirements of Part 36 of this chapter.

(b) Minimum weight. The minimum weight (the lowest weight at which compliance with each applicable requirement of this part is shown) must be established so that it is not less than—

(1) The lowest weight selected by the applicant;
(2) The design minimum weight (the lowest weight at which compliance with each structural loading condition of this part is shown); or
(3) The lowest weight at which compliance with each applicable flight requirement is shown.

More information-
http://adg.stanford.edu/aa241/structures/loads.html

An interesting video on the B777 wing loading test- http://youtu.be/Ai2HmvAXcU0

2) Can we derive some mathematical formula or equation to calculate / compute the Total Weight of the Machine (Airplane) before takeoff ?

Yes. Operating empty weight/OEW is the basic weight of an aircraft including the crew, all fluids necessary for operation such as engine oil, engine coolant, water, unusable fuel and all operator items and equipment required for flight but excluding usable fuel and the payload. Also included are certain standard items, personnel, equipment, and supplies necessary for full operations.

The OEW is basically the sum of the Manufacturer's Empty Weight/MEW, Standard Items/SI, and Operator Items/OI. This would include not only the crew weight but their suitcases/flight bags as well. Even the magazines in seatback pockets.

MEW + SI + OI = OEW

Therefore to get our weight for takeoff-
OEW + Fuel load + Passenger weights + Cargo weight = the actual Take Off Weight/TOW. Also, add or subtract adjustments required by the aircraft performance manual for nonstandard temperature/pressure, anti-icing use, aircraft configuration deviations/CDL (like a missing fairing) ect.

The heaviest allowable weight, providing there are no performance penalties or short flight structural limitations (Construction/Manufacturing limits are called "structural" limitations) like burning enough fuel to meet landing weight limits to be concerned about-

OEW + Max Fuel + Max Passengers + Max Cargo = Max Take Off Weight/MTOW

3) Should we add safety factor value to this total weight ?
There is a safety factor already added into the aircraft limitations. This is required by regulation for aircraft certification.

4) Do you feel electronic instrument panels calculating and showing the Total
Weight (Load) of the aircraft can be useful for Pilot before he takes a take off?

Any instrument is only as good as the input of feed. If the source of information is incorrect, like wrong values are entered in an FMS, than the information presented is useless. While some may consider such a thing useful, another instrument to tell you such information is not necessary. The FMS, if available, is quite sufficient provided all the correct values have been entered. Otherwise computer generated or old fashioned pen and paper weight & balance works fine.

...Alarms will buzz to the Cabin Crew if Overload occurs within the aircraft before the Take Off...

The "cabin crew" are the flight attendants. An alarm for the Flight Crew really isn't necessary if proper checks have been completed and the weight & balance verified.

5) Among different accidents, which are the most likely to occur because of Aircraft Overweight ?

1. During Takeoff.
2. During Landing.
3. During Aircraft flight (i.e. After Plane Takeoff and Before landing).

That is something I do not know. You would have to look at statistical data for accidents where weight was a factor, but I'd guess the takeoff phase. You might find more info at Http://www.aviationsafety.net or http://www.skybrary.aero/index.php/About_SKYbrary where you could do your own statistical research.

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D. Norkus

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I can address questions about airline pilot employment & entry level airline careers in the United States, women pilots, flight training, pilot certification, U.S. flight scholarships (mostly for women), aviation & airline safety topics, aviation accident investigation and airline operations. ***Please note, I cannot address flight training & career queries from outside the United States, or aero engineering degree programs/careers, aviation management topics. ****

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Airline captain with 15 years past experience in airline ground operations. I have previously flown as a commercial skydive pilot & ferry pilot and majored in Aviation Science


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Embry Riddle Aeronautical University; Aviation Safety/Accident investigation.

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