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Thread: Vs versus Vmca
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Old 12th Jul 2003, 16:17
  #10 (permalink)  
Tinstaafl
 
Join Date: Dec 1998
Location: Escapee from Ultima Thule
Posts: 4,273
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MJ

Light twins are not required to have any single engine climb performance in the landing or approach configurations. This means that if you decide to go around you can expect to lose some height while you accelerate to at least Vxse & reconfigure. At some point in the approach it becomes impossible to make an asymmetric missed approach without hitting the ground ie you must commit to a landing regardless. The height to do this varies with a/c type, weight & configuration, density altitude, pilot skill/currency & obstacles to be cleared on climb out.

This problem can be minimised by maintaining a low-ish drag configuration (eg wheels down but limit the amount of flap) & >Vyse for as long as possible. Allowing for a/c response time & skill, at some point you have to decide that a landing is a reasonable expectation, configure the a/c & reduce speed to achieve Vat. That point commits you to landing.

Additionally, under Oz rules, an instrument approach must not be commenced unless the a/c can maintain the missed approach climb gradient OR has the MDA/DA adjusted upwards so that the additional missed approach starting height + the achievable climb gradient give at least the same obstacle clearance. This can complicate things a bit...
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