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Commercial Airplane Operators
Commercial Airplane Op  
QUESTION: Dear Marc

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: There are two main factors in your question to be answered. Let's deal with the first. The takeoff weight is really based on the landing weight. How much weight can the airplane sustain when landing. This is not too critical when the aircraft has the ability to jettison fuel to lower the landing weight. Commercial airplanes only carry enough fuel reach it's destination or it's alternate destination plus 45 minutes. Is the rule in most cases. Most aircraft have over weight sensors to be checked if the airplane should land with some excess weight.
The next factor is runway length and height above sea level and temperature conditions. This has to do with the power available to lift the plane under these conditions. The air density effects the lift capabilities and also the engine power. Charts are written for individual aircraft. This a responsibly of the dispatcher that usually makes this information available to the captain.
Believe I answered your questions but would like to add another parameter. The take off weight alone may not of concern. The weight distribution also. What is the center of gravity on take off and how it is effected as fuel burns off. That is why the flight manual will contain a pertinent CG range for flight to assure the CG remains within the acceptable range. A nose heavy aircraft will require a little more runway to take off.
For more detailed information looking at the flight manual for each airplane will give you insight on the limitation for each aircraft that must be complied with by the carrier.

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

QUESTION: Dear Marc

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
I actually answered your question. Most of this information is in the aircraft's Flight manual.
In one of your questions. After all the engineering calculations, flight test are performed to see if those calculations were correct. However after many flight hours resonate frequencies of the aircraft could later cause mechanical failure that did not appear in the calculations or flight test results. A hard landing may not damage an aircraft visibly  but can stress an area that will fail at a later time. For a simple explanation of resonate frequency. Take a piece of metal and bend it back and forth eventually it will break. The smaller the motion the longer it will take to fail. These weak points can show up after years of flying.
Now lets talk about weight. Weighting the three points, nose and main gear. The mains are totaled but the nose is used to computer the center of gravity. Nose weight times the distance from the main gear that gives us the moment arm divided by the total weight now gives us the CG location at that weight. To make something perfectly clear. Even it this point is within the pertinent CG range. (remember I mentioned this before)the pilot may still not be safe because of how the weight was distributed. Under normal conditions this would be a factor. But let me give you a situation that can occur. Take off max weight cg is fine but the pilot makes a stop to drop off some freight but does not check his pertinent CG range. The weight may have been removed from a cargo hold that upsets the CG range. Can you see the picture now.
Your questions covered many scenarios. Nothing that can be cover in one session. You are looking for a complete education on the subject in one e-mail.  

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Marc Ebelini

Expertise

Basis aircraft and engine maintenance. Avionics and other electronic questions related to computers and radio communications.

Experience

FAA licensed comercial pilot, A&P mechanic, former authorized inspector, ground instructor certified in aircraft, powerplant and radio navigation. FCC commercial license.

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