V1 (speed)

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Aircraft take-off, without damage (dry runway) and damage before (dry) or after (wet) V 1

The decision speed ( English decision speed ) refers to the speed of a starting plane, to which a rejected take-off may take place. It is abbreviated internationally with .

General

According to the certification specifications (CS) of the European Aviation Safety Agency (EASA) , twin-engine and multi-engine feeder aircraft as well as large jet engine aircraft are subject to the regulations regarding the decision speed.

The decision speed is to be selected so that the respective aircraft can be brought to a complete standstill on the remaining runway section until this speed is reached after an aborted take-off , without using the thrust reverser . Since the decision-making speed depends on various parameters relating to the aircraft, the runway and the weather , it must be calculated individually for each aircraft and before each take-off.

Determining parameters

The speed of decision depends on various parameters. In addition to the total mass of the aircraft when taking off, the performance of the spoilers and landing gear brakes must also be taken into account. With regard to the runway, the take-off run available TORA as well as its coefficient of friction (rubber of the aircraft tires to the concrete or asphalt of the runway), which is influenced by the roughness of the runway and prevailing weather conditions such as rain and snow, must be observed . The air density also plays a role, as it influences both the lift generated on the wing and the thrust of the engines .

On a very long or on a (hypothetical) infinitely long runway, V 1 has an upper limit, despite the sufficient braking distance, which is set by the maximum permissible speed of the tires.

Actions after exceeding the decision-making speed

If the decision-making speed is exceeded and a technical defect occurs on the aircraft, the take-off may no longer be aborted. All commercial aircraft must be designed in such a way that they can successfully complete the take-off process even after one engine has failed if the decision-making speed has been exceeded using all engines. The safe take-off ( English takeoff safety speed ), which at a height of 35 feet is (10.67 meters) must be achieved so the failure of one engine. If the runway is wet, a lower rate of climb can be accepted in the event of a technical malfunction . B. needs to be reached at only 15 feet (4.57 meters). Aborting a take-off would be more risky than continuing the take-off with one after the failed engine has been exceeded .

Individual evidence

  1. ↑ EASA Certification Specifications for Normal, Utility, Aerobatic and Commuter Category Aeroplanes (CS-23), 3rd amendment of July 20, 2012, No. 23.51
  2. ↑ EASA Certification Specifications and Acceptable Means of Compliance for Large Airplanes (CS-25), 12th amendment of July 13, 2012, No. 25.107
  3. ^ A b c Niels Klußmann and Arnim Malik, “Lexicon of Aviation”, Springer Verlag, Berlin and Heidelberg, 3rd edition 2012, page 71, ISBN 978-3-642-22499-7
  4. ^ Heinrich Mensen, "Aviation Manual", Springer Verlag, Berlin and Heidelberg, 2003, page 847, Figure 5-3, ISBN 978-3-540-58570-1
  5. ↑ Claus Cordes, "Aborted start beyond theory", page 4 (PDF; 652 kB)

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