---------------------------------------------------------- Commander-List Digest Archive --- Total Messages Posted Sun 05/25/03: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:33 AM - Cheap ships (Nico van Niekerk) 2. 08:48 AM - Re: Cheap ships (William Boelte) 3. 10:46 AM - Re: Cheap ships (CloudCraft@aol.com) ________________________________ Message 1 _____________________________________ Time: 12:33:21 AM PST US From: "Nico van Niekerk" Subject: Commander-List: Cheap ships --> Commander-List message posted by: "Nico van Niekerk" Thanks, Chief, for the education on these engines. Your explanation was clear and well done. Got a couple of questions that bug me. Why would a Sabreliner 60SC Raisbeck 9 paz Jet be sold for $299K? Or an HS125-400 for under $500K? I can imagine that there could be time-out engines and other problems, such as non-compliance with noise (because those pods look awfully small in the pics) etc., but these birds hardly have 2000 hrs SMOH. It looks like good value for money but, one cannot help but wonder. Then, there are the MU's. An acquaintance got killed many years ago in an MU, supposedly a runaway trim caused it to pull up into a stall after takeoff and it crashed. Rumors are not my stock-in-trade but bad stories about the MU's keep filtering through the hanger talk. What's your take on it? Finally, what should one do when a trim runs away, pulling up all the time? If the circuit breaker doesn't pop (the ones that are flat and only pops when there's an overload on the circuit) should the pilot rather put the plane in a steep turn and deal with a high speed stall rather the one that brings the plane down? There should be a point in a steep turn where full up trim balanced with a certain amount of power would sustain flight in a continuous turn, even if it's just to give the pilot time to get a mental hold on the problem. How would you handle that? Thanks Nico ----- Original Message ----- From: Subject: Re: Commander-List: feathering > --> Commander-List message posted by: CloudCraft@aol.com > > In a message dated 05/21/03 08:41:57 Pacific Daylight Time, > nico@cybersuperstore.com writes: > > > > Is there a reason why some turboprops would feather their props at shutdown, > > and others not? > > > > We can divide the world of turbo props into 2 camps (with due respect to > Rolls Royce, Lycoming, Allison and Astazu) > > Garrett vs. Pratt & Whitney. > > Garretts (this week a subsidiary of AlliedSignal) are fixed shaft, axial flow > turbines, meaning the whole compressor / power turbine sections hang on a > common shaft, turning the gearbox that turns the prop. Air enters the front, > mixes w/ fuel, combusts and blows out the back. > > In order to start these engines, the starter/generator has to spin the whole > kit and kaboodle. A "feathered" prop would add more drag. This is why the > Garretts have "start locks" that below a certain centrifugal point, allow > pins to slide into place and hold the props at a very fine pitch during shut > down. (And why Garrett pilots hold the props in reverse during shut down: > to allow the start locks to extend and then let the blades come to rest on > them) > > Pratt & Whitney are reverse flow, free turbine engines. Air enters the back, > turns 180 degrees, combusts, turns the power turbine and then drives a second > turbine -- not connected to the power stage of the engine, driving the prop > gear box. (and then gasses exhaust via another 180 degree turn at the front > of the engine. > > So ... on the P&W engines, the prop in NOT connected to anything and thus the > starter doesn't care if it's in a high drag setting or not. > > Note: This could be confusing because as a multi engine pilot you think of > feather as a low drag configuration. Yes, it is ... while you're in flight. > Think of the engine start process and a feathered prop is lots of drag. > > As on a piston engine, low oil pressure lets the blades move to feather > position on turbo prop engines. > > P&Ws do this on shut down. Garretts have those start locks to hold the > blades from feathering during shut down. > > A sure way to burn up a Garrett engine is to start it w/ a feathered prop. > > Did I make this whole thing confusing enough? I can go on .... > > Wing Commander Gordon > > ________________________________ Message 2 _____________________________________ Time: 08:48:45 AM PST US From: "William Boelte" Subject: Re: Commander-List: Cheap ships --> Commander-List message posted by: "William Boelte" I don't know about your first two questions, but I have some experience with the third. I flew P-2 Neptunes in my first squadron. The P-2 had a very powerful pitch trim system called Varicam-- it was a complex electro-hydraulic system which when at full nose up trim in cruise flight required both pilots to push the elevator to its nose down stop and the nose would still rise up. Here are the procedures for "Full Runaway Up Varicam" "Reduce power to approx. 25 in. MAP Hold forward pressure on the yoke. Roll into moderate bank 20-30 degrees Lower full flaps. With these procedures carried out, the nose of the aircraft should fall through (assuming vertical has traveled full up) between 120- 130 knots IAS. Wings can then be leveled and power added to maintain 115- 125 knots IAS while holding forward yoke pressure an attempt is made to return the varicam to neutral using the procedures outlined under Manual Operation" We used to practice the procedure It works as advertised. Bill ----- Original Message ----- From: "Nico van Niekerk" Subject: Commander-List: Cheap ships > --> Commander-List message posted by: "Nico van Niekerk" > > Thanks, Chief, for the education on these engines. Your explanation was > clear and well done. > > Got a couple of questions that bug me. > > Why would a Sabreliner 60SC Raisbeck 9 paz Jet be sold for $299K? Or an > HS125-400 for under $500K? I can imagine that there could be time-out > engines and other problems, such as non-compliance with noise (because those > pods look awfully small in the pics) etc., but these birds hardly have 2000 > hrs SMOH. It looks like good value for money but, one cannot help but > wonder. > > Then, there are the MU's. An acquaintance got killed many years ago in an > MU, supposedly a runaway trim caused it to pull up into a stall after > takeoff and it crashed. Rumors are not my stock-in-trade but bad stories > about the MU's keep filtering through the hanger talk. What's your take on > it? > > Finally, what should one do when a trim runs away, pulling up all the time? > If the circuit breaker doesn't pop (the ones that are flat and only pops > when there's an overload on the circuit) should the pilot rather put the > plane in a steep turn and deal with a high speed stall rather the one that > brings the plane down? There should be a point in a steep turn where full > up trim balanced with a certain amount of power would sustain flight in a > continuous turn, even if it's just to give the pilot time to get a mental > hold on the problem. How would you handle that? > > Thanks > Nico > > > ----- Original Message ----- > From: > To: > Subject: Re: Commander-List: feathering > > > > --> Commander-List message posted by: CloudCraft@aol.com > > > > In a message dated 05/21/03 08:41:57 Pacific Daylight Time, > > nico@cybersuperstore.com writes: > > > > > > > Is there a reason why some turboprops would feather their props at > shutdown, > > > and others not? > > > > > > > We can divide the world of turbo props into 2 camps (with due respect to > > Rolls Royce, Lycoming, Allison and Astazu) > > > > Garrett vs. Pratt & Whitney. > > > > Garretts (this week a subsidiary of AlliedSignal) are fixed shaft, axial > flow > > turbines, meaning the whole compressor / power turbine sections hang on a > > common shaft, turning the gearbox that turns the prop. Air enters the > front, > > mixes w/ fuel, combusts and blows out the back. > > > > In order to start these engines, the starter/generator has to spin the > whole > > kit and kaboodle. A "feathered" prop would add more drag. This is why > the > > Garretts have "start locks" that below a certain centrifugal point, allow > > pins to slide into place and hold the props at a very fine pitch during > shut > > down. (And why Garrett pilots hold the props in reverse during shut > down: > > to allow the start locks to extend and then let the blades come to rest on > > them) > > > > Pratt & Whitney are reverse flow, free turbine engines. Air enters the > back, > > turns 180 degrees, combusts, turns the power turbine and then drives a > second > > turbine -- not connected to the power stage of the engine, driving the > prop > > gear box. (and then gasses exhaust via another 180 degree turn at the > front > > of the engine. > > > > So ... on the P&W engines, the prop in NOT connected to anything and thus > the > > starter doesn't care if it's in a high drag setting or not. > > > > Note: This could be confusing because as a multi engine pilot you think > of > > feather as a low drag configuration. Yes, it is ... while you're in > flight. > > Think of the engine start process and a feathered prop is lots of drag. > > > > As on a piston engine, low oil pressure lets the blades move to feather > > position on turbo prop engines. > > > > P&Ws do this on shut down. Garretts have those start locks to hold the > > blades from feathering during shut down. > > > > A sure way to burn up a Garrett engine is to start it w/ a feathered prop. > > > > Did I make this whole thing confusing enough? I can go on .... > > > > Wing Commander Gordon > > > > > > ________________________________ Message 3 _____________________________________ Time: 10:46:43 AM PST US From: CloudCraft@aol.com Subject: Re: Commander-List: Cheap ships --> Commander-List message posted by: CloudCraft@aol.com In a message dated 05/25/03 00:33:54 Pacific Daylight Time, nico@cybersuperstore.com writes: > Why would a Sabreliner 60SC Raisbeck 9 paz Jet be sold for $299K? Or an > HS125-400 for under $500K? I can imagine that there could be time-out > engines and other problems, such as non-compliance with noise (because those > pods look awfully small in the pics) etc Nico, Your powers of observation are spot on! It is the engines. The Sabers, Jet Commanders, early Hawkers, Jet Stars, Lears, etc., were powered by "straight pipe" turbo jets. Those ear shredding engines are not able to operate in most of the civilized world excepting on MediVac flights or some off some runways (if the airport will allow) where reduced thrust take-offs can fit those airplanes into Stage III climb noise limits. So there are a bunch of airframes waiting for some great re-engine idea. Just like our Commanders. As far as the MU-2 goes, I have to be very cautious because I've never flown one and I hate speculation and rumor mongering. That being said, let me speculate and rumor monger. The MU-2 series have spoilers rather than ailerons and the short body models are "short coupled" in terms of pitch control. The MU-2s are fitted with Motorola / Bendix M-4 series autopilots. These are very strong auto pilots ... I've been told they were placed on the C-130 as well as our Commanders. It's theorized, as you hinted at, that an MU-2 can get out of trim during a flight and when the pilot disengages for landing or the A/P faults and disconnects, the MU-2 will do some shocking maneuvers. Note that most MU-2 accidents are on final or final approach, near the airport -- maybe the transition point from A/P engaged to uncoupling. I'll take this moment to remind everyone with an autopilot to disconnect at top of climb / acceleration and re-trim. Probably once an hour to accommodate CG shift and again in descent. The pitch trim run away recovery is kind of airplane specific and your idea, plus Bill's treatment of the S-2 are typical. But you know, there are usually many ways to depower an A/P. The yoke disconnect switch, the A/P control head often has a power switch, the circuit breaker and if it's Day and you're not solid IFR (or maybe if you are ...) the Master Switch. In terms of the MU-2, the guys who I've talked with that teach the airplane say it's probably the "surprise" attitude the airplane takes when the A/P disconnects rather than the A/P flying into an unusual attitude. Wing Commander Gordon