The manufacturers procedures are usually well thought-out; the implementation by regulator or operator not always so, e.g. some Regulators declare manufacturers ‘advice’ (non mandatory guidance in manufacturers operations manual) as mandatory in lieu of independent thought (and escaping the lawyers).
If the AFM contains ‘mandated’ procedures then there are good reasons for them; the manufacture is usually guilty of not explaining these reasons in other documentation. AFM procedures are the legal requirements and must be followed; only the manufacture or regulator can change these or give a dispensation.
Many aircraft with auto deployed systems require a manual follow up to counter system failure (which could be the reason for an RTO), or operating error. The sequence of a procedure may consider the ease or time of the crew selection, or the timing of an ‘automatic’ interlock to be made, e.g. time for the engine spool-down before reverse can be selected.
Other considerations may include the effectiveness of the retarding device (normally brakes are the best), or the certification requirements where the certificated stopping distance is not always dependent on the use of reverse, whereas spoilers are. Also the logic in using controls is considered; it may be easier to continue to hold the thrust levers after retardation in order to engage reverse and modulate the thrust level.
Check the wording carefully between AFM and manufactures ops manual, ask the manufactures advice, try to educate the regulator, and always stand on the brakes.
Last edited by alf5071h; 19th September 2004 at 21:26.