round_peg Posted June 21, 2011 Report Share Posted June 21, 2011 I have just become the co-owner of a 2006 CTsw (yes, congratulations are in order). We are still awaiting delivery and in the meantime I'm trying to figure out some of the transition issues (from a Cessna 172). The one that's bugging me right now is cruise performance. The old Cessna came with a table of BHP, RPM and TAS for a variety of throttle settings and altitudes. I was able to interpolate and expand this table and I found it to be really helpful for flight planning and fuel management. I find a real paucity of similar data for the CT. The POH is really sparse. Can anyone help with this question, or tell me why the CT makes it unnecessary? Thanks! Link to comment Share on other sites More sharing options...
johngpilot Posted June 21, 2011 Report Share Posted June 21, 2011 go here on Flight Design USA web site (for CTLS/sw) http://flightdesignusa.com/flight-training/student-pilots/ Called "Performance " the document number is AF04300006_00.pdf Link to comment Share on other sites More sharing options...
round_peg Posted June 21, 2011 Author Report Share Posted June 21, 2011 go here on Flight Design USA web site (for CTLS/sw) http://flightdesignusa.com/flight-training/student-pilots/ Called "Performance " the document number is AF04300006_00.pdf Thanks for the quick reply! That document is perfect, but it's for the CTLS. Close enough for government work? Link to comment Share on other sites More sharing options...
johngpilot Posted June 21, 2011 Report Share Posted June 21, 2011 Thanks for the quick reply! That document is perfect, but it's for the CTLS. Close enough for government work? They are very close and if you are cutting it that close you will be at 6-7 hours of flight anyway so ...Time for a break DONT RUN OUT OF GAS. . Caps intentional... Link to comment Share on other sites More sharing options...
round_peg Posted June 21, 2011 Author Report Share Posted June 21, 2011 They are very close and if you are cutting it that close you will be at 6-7 hours of flight anyway so ...Time for a break DONT RUN OUT OF GAS. . Caps intentional... Always good advice...! No, not a matter of cutting it close but more a matter of liking the knowledge of what RPM settings are needed to maintain a given BHP at a given altitude, and the resulting TAS. Total pilot geek stuff. Link to comment Share on other sites More sharing options...
coppercity Posted June 22, 2011 Report Share Posted June 22, 2011 I have owned and flown both all over the country, the CTLS performance chart will get you within a knot or two. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 22, 2011 Report Share Posted June 22, 2011 ... The old Cessna came with a table of BHP, RPM and TAS for a variety of throttle settings and altitudes... the old cessna had a fixed pitch prop, the ctsw has a ground adjustable prop. performance is the result of a prop pitch / rpm ratio. i suggest that you begin flight planning for a 5 gph fuel burn and refuel when down to 10 gallons. you can get more precise if you need to after you see what your performance is at your prop setting. IOW plan on a fuel stop at 575nm Link to comment Share on other sites More sharing options...
round_peg Posted June 22, 2011 Author Report Share Posted June 22, 2011 the old cessna had a fixed pitch prop, the ctsw has a ground adjustable prop. performance is the result of a prop pitch / rpm ratio. i suggest that you begin flight planning for a 5 gph fuel burn and refuel when down to 10 gallons. you can get more precise if you need to after you see what your performance is at your prop setting. IOW plan on a fuel stop at 575nm I know, one of the new items to consider is the adjustable prop pitch. However... the CTLS performance table doesn't specify a prop pitch. One thing that jumps out at me looking at this table is that the Rotax doesn't require as much throttle adjustment to maintain a given power output, compared to the tractor engine in the Cessna. Fuel consumption and TAS hardly changes either. So maybe it's a total non-issue with the CT. Link to comment Share on other sites More sharing options...
207WF Posted June 27, 2011 Report Share Posted June 27, 2011 I can't believe the performance chart. If 5500 rpm at 3000 feet is 100% power, it seems there is no way you can pull 83% power at 12,000 feet using 5200 rpm. Is this for the 914 turbo? WF Link to comment Share on other sites More sharing options...
wlfpckrs Posted June 27, 2011 Report Share Posted June 27, 2011 After flying the CTsw, you'll want to throw rocks at the 172. Link to comment Share on other sites More sharing options...
round_peg Posted June 29, 2011 Author Report Share Posted June 29, 2011 I can't believe the performance chart. If 5500 rpm at 3000 feet is 100% power, it seems there is no way you can pull 83% power at 12,000 feet using 5200 rpm. Is this for the 914 turbo? WF I was prepared to accept that the Rotax and the Lycoming are two very different engines, and leave it that -- but for curiosity's sake if nothing else, I'd also like to know the answer to this question. Link to comment Share on other sites More sharing options...
Roger Lee Posted June 30, 2011 Report Share Posted June 30, 2011 It could be based on a 914 and maybe a 912 too if it has an in flight adjustable prop that can be set to 5800 WOT. Rotax bases their figures on an engine that can get 5800, which we can't. The figures in the manuals are not set up for engines that only get 5500 rpm WOT. You have to remember when looking at a manual that these engines go on all sorts of aircraft worldwide and not just the US and on all types of aircraft. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 30, 2011 Report Share Posted June 30, 2011 but rog, a normaly asperated engine cannot achieve 83% at 12,000' its more like 3% x 12 = 36% reduction and that would be if you were getting 5,800 @ 12,000' WOT ( a pitch setting that wouldn't be useful ) you would be limited to ~ 64%, next adjust for 5,500 max and coarser pitch and you will be under 60%. Link to comment Share on other sites More sharing options...
Roger Lee Posted June 30, 2011 Report Share Posted June 30, 2011 Hi Ed, I knew I hated math and I stand corrected and remove maybe the 912. Since I didn't do any figuring that was why I said maybe the 912. I our manuals many items are mixed with the 912UL, 912ULS and the 914 Turbo so you need to read and separate out which one you are looking at. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted June 30, 2011 Report Share Posted June 30, 2011 if i fly over to allen's field, columbia, 12,500 would be an altitude where you could still be close to terrain. with the rotax i like to remind myself that i have ~55hp available in case the need to climb becomes critical. Link to comment Share on other sites More sharing options...
207WF Posted July 13, 2011 Report Share Posted July 13, 2011 I think I just partially figured out the problem with the FD cruise performance chart. The % power shown, like the 83% figure I did not believe, is actually stated as the percent of MCP (maximum continuous power). Roger's chart from Rotax shows that max continuous power, at 5500 rpm, is 90% of max power at 5800 rpm (at sea level). That suggests that the 83% in the FD chart is really only 83% of 90%, or 74.7% power. That still seems like too much for 12,000 DA. So, I want to interpret the 83% as 83% of the max continuous power that would be available at 12,000 feet (which might be only about 55% power). If you look in the FD chart it also shows 5500 rpm at 3,000 DA as 100% MCP. I want to interpret this as having your prop pitched that way. (Roger's ideal if I usually cruise at 3,000.) So, it says that if you pitch your prop that way and go to 12000 DA, it takes 83% of full throttle (assuming power is linear in throttle) to get 120 knots true at 5.2 gph. That does seem pretty close! The thing that I still don't get is that the chart says you are generating 77 hp at that setting, which seems way too high. WF Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted July 14, 2011 Report Share Posted July 14, 2011 the mcp does change things by about 8% IIRC. it cannot help you make sense of this chart, this chart is really, really wrong. its way off on hp but perhaps close on speed, i think its overstating fuel burn at altitude as well. Link to comment Share on other sites More sharing options...
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