Hi all, after discussing turbine starting procedures with a real-life BK117 pilot I want to give you some corrections and additions which are very interesting after my opinion. I know that Melchior Franz has his own sources but I address all those others who read my last statement and might be misinformed:
Some short technical remarks Modern helos are equipped with a two shaft turbine with air compressing part (gas producer, N1) and free-running working part(N2). These two parts are only connected by the airflow through the turbine, there is no gear or any mechanical connection between. EVERY turbine is connected through a free wheel with the main gear (defective turbine, autorotation, ..). The rotor drives main gear and connected tailrotor and hydraulic pumps(!!!, stearing) when autorotating. Rotor brake: BK117 (BO105???): is placed on the tailrotor drive near the main-gear. It is NOT constructed like a car emengency brake (loosen-fasten) but has a hydraulic system with a valve which reduces pressure after some time so there is not permanent fastening of the rotor system. So with the BK117 there is no real danger from the rotor brake when staring the engines as none would apply pressure on the rotorbrake an THEN start the engine. Starting procedure of turbines: [Electrical supply is on, some BK117 have different systems, ie. main power switch, batt switch, shed bus switch] Fuel pumps on (BK117: only as booster pumps until turbines are running, turbines drive own mechanical fuel pumps. BO105: requieres running fuel pumps all the time due to fuel tank construction. Otherwise lacking supply causes abrupt shutdown of turbines if alarms are not recognized - real life proofen, caused autorotation into water and lost of helo/not lifes) BK117: throttle is on "0" position. You use the electrical starter to get the gas producer (air compressing part, N1=Ng) to 10% N1 rpm, then move throttle ca. half way to "idle" position -> trigger for automatic ignition (BK117, BO105 requires manual ignition). Hold starter button, when 25% N1 is reached N2 must increase and rotor movement visible - otherwise failure, stop starting procedure. TOT (T4) can be modified during the turbine running-up procedure by adapting throttle position. Check maximum TOT (turbine outlet temperature, 650 C deg BK117, BO105 might be a little hotter), don't exceed, stop starting procedure. Release starter button when 40% N1 is reached. Move throttle full to "idle" position, turbine rpm increases automatically to 68% N1 (idle). N2 and rotor rpm follow to normal rpm When turbine rpm has stabilized set generator "on" (identical starter and generator engine, same switch with pos [starter - none - generator]). If no extern power supply wait until batterie recharge current decreases from ca. 150 to 100 Amps Do same procedure for engine 2. Before flight: Slowly turn throttles to "flight" position - for each engine Georg "HeliFLYer" EDDW --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.756 / Virus Database: 506 - Release Date: 08.09.2004 _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
