-VS, which corresponds to the conventional stall (i.e. when the lift suddenly collapses). At that moment, the load factor is always less than one (FAR 25 reference stall speed). 

Figure B6: CL versus Angle of Attack 

“JAR 25.103 Stall speed 

(a) The reference stall speed VSR is a calibrated airspeed defined by the applicant. VSR may not be less than a 1-g stall speed. VSR is expressed as: 

Where: VCLMAX = [speed of maximum lift coefficient, i.e. VS1g] nzw = Load factor normal to the flight path at VCLMAX” 

Change 15 of JAR 25 (October 2000) introduced this notion of reference stall speed VSR, which is the same as Vs1g. In the previous version of JAR 25, a direct relationship between VS and VS1g was provided, in order to ensure the continuity between aircraft models certified at Vs, and aircraft models certified at VS1g. 

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For JAR, this rapport between Vs and Vs1g is: 

As an example (refer to the “Takeoff” chapter): 

. For aircraft models certified at VS (A300/A310), V2min = 1.2 VS 

. For aircraft models certified at VS1g (Fly-By-Wire aircraft), V2min = 1.13 VS1g 

IMPORTANT: In Airbus operational documentation, as well as in this brochure,VSR is referred to as VS1g. 

“FAR 25.103 Stalling speed 

(a) VS is the calibrated stalling speed, or the minimum steady flight speed, in knots, at which the airplane is controllable, with Zero thrust at the stalling speed, or […] with engines idling”. 

FAR 25 doesn’t make any reference to the 1-g stall speed requirement. Nevertheless, Airbus fly-by-wire aircraft have been approved by the FAA, under special conditions and similarly to JAA approval, with VS1g as the reference stall speed. 

2. MAXIMUM STRUCTURAL WEIGHTS 

2.1. Aircraft Weight Definitions 

. Manufacturer’s Empty Weight  (MEW) : The weight of the structure, power plant, furnishings, systems and other items of equipment that are considered an integral part of the aircraft. It is essentially a “dry” weight, including only those fluids contained in closed systems (e.g. hydraulic fluid). 

. Operational Empty Weight (OEW) : The manufacturer’s weight empty plus the operator’s items, i.e. the flight and cabin crew and their baggage, unusable fuel, engine oil, emergency equipment, toilet chemicals and fluids, galley structure, catering equipment, seats, documents, etc… 

. Dry Operating Weight (DOW) : The total weight of an aircraft ready for a specific type of operation excluding all usable fuel and traffic load. Operational Empty Weight plus items specific to the type of flight, i.e. catering, newspapers, pantry equipment, etc… 

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. Zero Fuel Weight (ZFW) : The weight obtained by addition of the total traffic load (payload including cargo loads, passengers and passenger’s bags)  and the dry operating weight. 

. Landing Weight (LW) : The weight at landing at the destination airport. It is equal to the Zero Fuel Weight plus the fuel reserves. 

. Takeoff Weight (TOW): The weight at takeoff at the departure airport. It is equal to the landing weight at destination plus the trip fuel (fuel needed for the trip), or to the zero fuel weight plus the takeoff fuel (fuel needed at the brake release point including reserves). 

TOW = DOW + traffic load + fuel reserves + trip fuel LW = DOW + traffic load + fuel reserves ZFW = DOW + traffic load 

Figure B7 shows the different aircraft’s weights, as defined in the regulations: 

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2.2. Maximum Structural Takeoff Weight (MTOW) 

The takeoff weight (TOW) must never exceed a Maximum structural TOW (MTOW) which is determined in accordance with in flight structure resistance criteria, resistance of landing gear and structure criteria during a landing impact with a vertical speed equal to -1.83 m/s (-360 feet/min). 

2.3. Maximum Structural Landing Weight (MLW) 

The landing weight (LW) is limited, assuming a landing impact with a vertical speed equal to -3.05 m/s (-600 feet/min). The limit is the maximum structural landing weight (MLW). The landing weight must comply with the relation: 

actual LW = TOW – Trip Fuel ≤  MLW 

or 

actual TOW ≤   MLW + Trip Fuel