landing, just carry on. Propeller Overspeed If engine control is lost and RPM rises above the maximum, reduce power, raise the nose and hope reduced airspeed gets things under control. If the CSU is not working, feathering immediately may leave you with a shut down engine in fully fine pitch, though it does depend on the aircraft (Doves, apparently, have a separate feathering motor). If you're not quick enough, damage could be caused from over-revving and the feathering system may not cope with the extreme RPM. DO NOT attempt to unfeather the engine but land as soon as possible. Techie Stuff 247 Failure of Feathering System Most feathering systems don't function below a certain low RPM (typically 700-1000), so you don't start with the blades feathered. However, there are further implications—if your engine fails through a major mechanical fault, you may not be able to catch the propeller quickly enough. The usual reaction is to close the throttle of the dead engine first, so opening it a little may increase the RPM for feathering to take place properly. Keeping your speed up may help as well. If the propeller fails to feather, reduce your airspeed to a minimum (but not below scheduled engine-out climb speed) and allow the RPM to stabilise as low as possible. Try again. If feathering still fails, try to reduce speed so the rotation ceases, which will cause less of a drag penalty than a windmilling prop, even if it has stopped in fine pitch. Not only will your single-engined climbout performance be affected, directional controllability will be, too, though you should be OK down to Vmca. Twins Flying twin-engined helicopters requires a different philosophy in many ways, certainly getting used to not dumping the collective every time an emergency happens, and their complexity, although there is no real change in flying characteristics as there would be if an engine fails in an aeroplane. You also have takeoff and landing profiles, in case something happens, and performance charts, with generally more shallow approaches to comply with them. The regulations require you to ensure that your aircraft has adequate performance for any proposed flight. The "performance" of an aircraft describes its ability to maintain certain rates of climb against distance, so you can avoid hard objects (obstacles), particularly when you can't see them. As a result, the charts will emphasise rates and angles of climb very strongly (climb requirements are established with one engine working hard for a specified time). There are reasons for multiple engines, of course. One is that you get more power and can lift more, but another is for safety – failure of an engine should not affect the continued safe operation of the flight, or the other one, which is why there are isolation arrangements in the engine compartment. It follows, therefore, that the less the weight of the machine, the better it can fly with less power. In fact, with reference to the profiles above, you may find different max all-up weights for helipads and clear areas (there is no definition of a "helipad" for performance purposes – rather, it's any area that isn't a clear area, or one that allows operation inside your chosen performance group). The take-off and landing phases of any flight are the most critical, demanding the highest skills from crews and placing the most strain on the machine. Because of this, strict regulations govern the information used for calculating take-off or landing performance. Of course, in the old days (say during the war, or when the trains ran on time), having 248 Operational Flying enough engines to lift the load was all that mattered and no priority was given to reserves of power and the like. Now it's different, and you must be able to keep your machine a specified distance away from obstacles and be able to either fly away or land without damage to people or property (and the machine) if an engine fails. Performance requirements will be worked out before a C of A is issued, over a wide range of |