Re: [Flightgear-devel] c150 low G.
Dave Martin wrote: On Friday 28 October 2005 02:03, Vassilii Khachaturov wrote: In a real gravity-fed Cessna, there are 2 aspects relevant to the engine problems resulting from negative Gs that I was told about by the instructors. One is the fuel flow (tanks/carb/engine intake manifold) and the other is the oil flow that has gravity-induced return of the oil into the sump. If that stops, it's as disastrous as oil leak --- permanent damage can be done. (As opposed to just engine out due to momentary fuel absense which goes away as soon as one pulls back up and the gravity is restored). This is quite true but it only becomes a problem after a few seconds of sustained *negative* G as opposed to zero G. (Some 152 Aerobats have inverted oil systems to prevent this all together). I have more information on the survivability of engines starved of oil but it's probably not relevant here ;) As for the clearing the climb path, I was told to do some gentle S-turns rather than pushing over the nose in order not to screw up the airspeed and hence the time-to-climb calculations, as well as be less nauseating for the passengers (of course, if executed in a properly coordinated matter). We were training in a busy traffic area (EGBE UK) where other aircraft in unexpected places were a regularity. Typically we would make one check before reaching 650' QNH and turning crosswind. The trick to making the check is to leave the trim set to climb and just push forward momentarily while scanning ahead for anything resembling your own aircraft. Typically, aircraft would re-stabilise in its nominal climb in 10 seconds or so - not an issue when climbing for the training circuit. I can quite safely say that while you would have 'your heart in your mouth' as you pushed forward, it was certainly not even a zero-G motion and the engine certainly wouldn't waiver. Also, in low-G manouvers such as a high-AoA entry to an incipient spin or a 0-G pushover where very low positive G (certainly lower than 0.3G) is sustained for maybe 2 to 3 seconds, the engine would behave as in the cruise. Having flown the manouvers during PPL training (not required but none the less useful) I am adamant that the IO-200 will experience no power-loss down to a small fraction of a G even when sustained for several seconds. Thanks for the feedback, I'll change that. Harald. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] c150 low G.
..one check before reaching 650' QNH and turning crosswind. Just re-read my mail this-morning. Worryingly, thats not the first time I've confused QNH and QFE. Hmm, I don't remember the ground being *that* close in the circuit. ;) -- Dave Martin http://museum.bounce-gaming.net ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
[Flightgear-devel] c150 low G.
Just been having a muck about with the C150, apart from the low weight due to lack of pilot mass, I've been flying it much like I used to fly the real thing. One thing we used to do on climbout was 'clear ahead', just push the nose down for a moment to check we weren't about to eat another aircraft. When this is done on the FG c150, the engine stutters (FDM program fuel starvation on neg-G?) According to the HUD, it stutters at about +0.30G. In the real aircraft, we could make 0G manouevers that could last for a couple of seconds without the engine missing. -- Dave Martin http://museum.bounce-gaming.net ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] c150 low G.
When this is done on the FG c150, the engine stutters (FDM program fuel starvation on neg-G?) According to the HUD, it stutters at about +0.30G. In the real aircraft, we could make 0G manouevers that could last for a couple of seconds without the engine missing. In a real gravity-fed Cessna, there are 2 aspects relevant to the engine problems resulting from negative Gs that I was told about by the instructors. One is the fuel flow (tanks/carb/engine intake manifold) and the other is the oil flow that has gravity-induced return of the oil into the sump. If that stops, it's as disastrous as oil leak --- permanent damage can be done. (As opposed to just engine out due to momentary fuel absense which goes away as soon as one pulls back up and the gravity is restored). I have no clue as to quantitative charasteristics of the two and which one happens first. (Sorry I don't have time for more research at the moment). As for the clearing the climb path, I was told to do some gentle S-turns rather than pushing over the nose in order not to screw up the airspeed and hence the time-to-climb calculations, as well as be less nauseating for the passengers (of course, if executed in a properly coordinated matter). V. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] c150 low G.
On Friday 28 October 2005 02:03, Vassilii Khachaturov wrote: In a real gravity-fed Cessna, there are 2 aspects relevant to the engine problems resulting from negative Gs that I was told about by the instructors. One is the fuel flow (tanks/carb/engine intake manifold) and the other is the oil flow that has gravity-induced return of the oil into the sump. If that stops, it's as disastrous as oil leak --- permanent damage can be done. (As opposed to just engine out due to momentary fuel absense which goes away as soon as one pulls back up and the gravity is restored). This is quite true but it only becomes a problem after a few seconds of sustained *negative* G as opposed to zero G. (Some 152 Aerobats have inverted oil systems to prevent this all together). I have more information on the survivability of engines starved of oil but it's probably not relevant here ;) As for the clearing the climb path, I was told to do some gentle S-turns rather than pushing over the nose in order not to screw up the airspeed and hence the time-to-climb calculations, as well as be less nauseating for the passengers (of course, if executed in a properly coordinated matter). We were training in a busy traffic area (EGBE UK) where other aircraft in unexpected places were a regularity. Typically we would make one check before reaching 650' QNH and turning crosswind. The trick to making the check is to leave the trim set to climb and just push forward momentarily while scanning ahead for anything resembling your own aircraft. Typically, aircraft would re-stabilise in its nominal climb in 10 seconds or so - not an issue when climbing for the training circuit. I can quite safely say that while you would have 'your heart in your mouth' as you pushed forward, it was certainly not even a zero-G motion and the engine certainly wouldn't waiver. Also, in low-G manouvers such as a high-AoA entry to an incipient spin or a 0-G pushover where very low positive G (certainly lower than 0.3G) is sustained for maybe 2 to 3 seconds, the engine would behave as in the cruise. Having flown the manouvers during PPL training (not required but none the less useful) I am adamant that the IO-200 will experience no power-loss down to a small fraction of a G even when sustained for several seconds. -- Dave Martin http://museum.bounce-gaming.net ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
