Guest Maj Millard Posted January 2, 2011 Posted January 2, 2011 David, Ground speed is far from irrelevent, as it is what gets you there in the end. True airspeed readings are only accurate for cross country use in still air, which like hens teeth, is a rare commodity most of the time. Actual ground speed is required to accuratly compute time of arrival at destination, and expected fuel-burn for the distance. It is rare during cross-country flight of any distance, to not have any head, or tail winds. It is then that actual computed groundspeed is what matters.................................................Maj...
Guest Maj Millard Posted January 2, 2011 Posted January 2, 2011 Correct, GS is irrelevent if you just want to know how fast the aircraft will slip through the air, at a certain power setting. Best done in still air first thing in the morning for accuracy. That info is always available to you anyway, just subtract your indicated airspeed from the groundspeed figure on the GPS = airspeed at the time, also lets you know if it is a headwind or a tailwind...or none if they match, in which case it's true airspeed isn't it ?......................................................................Maj...
frank marriott Posted January 2, 2011 Posted January 2, 2011 Ross, TAS is the IAS corrected for altilude and temp. - Use your circular flight comuter [PRAYER WHEEL] - Some GA alitmeters have a subscale on them to set the OAT and read off the TAS. Has nothing to do with still air. TAS is used as a constant at a given IAS and density alitiude - the others are variables. Forecast winds are so unreliable at low altiudes I find the best way for navigation purposes is to plan TAS and recalulate with known GS once at cruise altitude [exception obviously with 20plus kts head winds forecast] All is good so long as you get there with reserves - my comment was about aircraft performance only, nothing to do with navigation. cheers Frank
Guest gazzawh Posted January 2, 2011 Posted January 2, 2011 Hi coolair I know of a number of VG Xls and a couple of the S models flying and under construction, congrats on getting yours up and flying. the stats refered to in the original kit plane source book (175 flying) are all US numbers as are the performance figures which are in statute miles per hour not Knots it would be interesting to know exactly how many Savvy's are currently flying and under construction in Aus. The only performance numbers that really matter are the one's you get when you are flying your aircraft. I get 83 knots IAS at 5000 rpm, Happy flying!! I completed a Savannah VGW in June 2010. My max true airspeed in level flight (100hp Rotax at 5400 RPM) is: 100 MPH - 87 Knots per hr - 160 Km per hr. This was verified by GPS in a four leg course. My single person (beginner) built time was about 800 hrs.I question the number of flying XL/VGW - 175. I have never met or talk to or heard about any other flying XL/VGW's - other than distributor demo's.
eightyknots Posted April 21, 2012 Author Posted April 21, 2012 I get 83 knots IAS at 5000 rpm, Happy flying!! That's around eighty knots: sounds like my kind of speed gazza.
Planechaser Posted June 2, 2012 Posted June 2, 2012 Always interested in the Sav thread as I all but flipped a coin between the Foxbat Ls and a Sav. Trawling through the thread I am a little surprised at the quoted speeds/power settings, like 87kts@5400. I was under the impression that the Sav lined up with the Bat for TAS. What I mean to say is with full fuel, 10kg in the back, and me( say 100kg! :{) ) I regularly get 87kts-90kts @ 4900rpm. Morning, no wind. When I say average I mean average, so 25 hrs into a service as regards oil, air filters, bug factor etc. The prop is set not far back from a crackle, for STOL ops, tundra tires, no spats. This is my standard config for a water run, which happens around 8am. Two other points to add to this are unless conditions are like skating on glass, anything over 90kts in academic, as the horse spends all it's time trying to buck you off, if you know what I mean!! The other is that wind always seems to slow me down more that it speeds me up. A head wind of 15kt will always turn into a 12kt tail wind. Gets me every time. Perhaps the Garmin Gremlin just likes bending my head! ;)
eightyknots Posted June 2, 2012 Author Posted June 2, 2012 Also some of the best cruisers that I have flown have a tendenacy to want to 'get on the step' in cruise. the Lightwing is very good at that, and getting on the step can make a lot of difference to speed/time over a leg , and also fuel burnt. My 582 Drifter also did it well. Basically at cruise speed you trim the nose down to a point where the wing is running a very low angle of attack, yet you still manage to not lose altitude. The wing in this mode is at it's lowest drag, hence the more efficient cruise profile. Because of the washout in the wing, the tips may be at or below 0 deg angle of attack (less drag) and the plane is flying along quite happy on the inboard sections of the wing, and any lift created from the fuselage and tail. This is a very basic explanation, as it is more of a feel thing, some planes have it ...others don't..................................................................Maj... Maj, in your experience, is it possible to get the Savannah 'on the step' for cruise or does this apply mainly to other aircraft? Always interested in the Sav thread as I all but flipped a coin between the Foxbat Ls and a Sav. Apart from flipping a coin, were there any other factors why you ended up buying a Foxbat/Valor/A22? Always interested in the Sav thread as I all but flipped a coin between the Foxbat Ls and a Sav.Trawling through the thread I am a little surprised at the quoted speeds/power settings, like 87kts@5400. I was under the impression that the Sav lined up with the Bat for TAS. What I mean to say is with full fuel, 10kg in the back, and me( say 100kg! :{) ) I regularly get 87kts-90kts @ 4900rpm. Morning, no wind. When I say average I mean average, so 25 hrs into a service as regards oil, air filters, bug factor etc. The prop is set not far back from a crackle, for STOL ops, tundra tires, no spats. I'm not sure where you obtained the 87 knots @ 5,400 revs figures. From what people tell me, the Savvy cruises at that speed with less revs (and less fuel consumed). Gazzawh in post #29 above achieves 83 knots @ 5,000 revs for instance and he flies a Savannah VG. I am really not sure whether the slightly larger but more aerodynamic XL or S models fly a bit better than that. Perhaps someone who flies the newer variants regularly could tell us whether the more sloping windscreen, etc, has paid off in better performance. I would be interested to know.
eightyknots Posted June 2, 2012 Author Posted June 2, 2012 The other is that wind always seems to slow me down more that it speeds me up. A head wind of 15kt will always turn into a 12kt tail wind. Gets me every time. Perhaps the Garmin Gremlin just likes bending my head! ;) It's Mr Murphy who is responsible for this! 1
damkia Posted June 2, 2012 Posted June 2, 2012 It's Mr Murphy who is responsible for this! It's like the weather forcasts....they are always right...........................................................eventually. 1
Planechaser Posted June 2, 2012 Posted June 2, 2012 Apart from flipping a coin, were there any other factors why you ended up buying a Foxbat/Valor/A22? I guess at the end of the day it came down to a personal preference. I had been mooning over the Zen 701 for a few years, and then discovered the Sav. All looked right with the world, and then when the opportunity cameup, so did the Foxbat. When I lined the two up side by side, the Bat won, but nothing you could really put your finger on. One thing surprising me at the moment, and it is more my impression than any strong facts, is the number of Bats Vs Savs used for flight training. I wouldn't have thought there wasn't much between them as aircraft, and the Sav is cheaper, or was last time I looked.
Kyle Communications Posted June 2, 2012 Posted June 2, 2012 Well I am a real expert here ( X being the unknown factor and Spurt being a drip under pressure ) so take what I write with a grain of salt for the moment. My Sav flew last sunday for the first time I was going through the flight log this morning on my Brauniger panel to see the info for the 3 flights on last sunday and at this stage my prop is a little coarse at the moment and probably needs to come back a degree but the max speed during the 3 flights was 94 knots 91 and 91 max engine rpm was 5400 and 5180 and 5160 so thats so far. Mind you I have flown her for a whole 39mins and 2 flights just basically around Ycab and a few circuits. I will let you know what I end up with I am going to repitch the prop tomorrow ready for when I can fly again...this weather is crap here for the next 4 days or so. Mind you I don't know why the 5400 was there on the test flight as I can't seem to get those rpm on my 2 flights Mark
Planechaser Posted June 2, 2012 Posted June 2, 2012 Mind you I don't know why the 5400 was there on the test flight as I can't seem to get those rpm on my 2 flightsMark I've got MGL Digital dials in the Bat, and sometimes you will see the RPM flick up to 5400 if you are running around the 5000-5100 mark. Seems to happen when it's gusty, so I am guessing that the wind gusts feed back through the prop and move the RPM around, and with and old school dial with propper damping on it, it just never shows up. The bat is flat out at just under 5300 in normal conditions. Well, that's my theory anyway....
Kyle Communications Posted June 2, 2012 Posted June 2, 2012 Thanks for that Plane chaser I was going to set it for around 5300 to 5400 flat out in level flight so will adjust the pitch about 1 deg at a time. Originally when I did my first full power run I could only get 4900 on the ground so I decreased the pitch 1 deg and got 5080 on the ground so looks like gain 100 to 150 rpm in the air so slowly slowly catch the monkey will do another degree.
Kyle Communications Posted June 2, 2012 Posted June 2, 2012 How do you find the MGL stuff....do you have any sort of EFIS in there or just the separate single digital gauges. I have been looking around at EFIS and the MGL stuff is very good pricing a fair bit cheaper than the rest
Gundy Posted June 2, 2012 Posted June 2, 2012 Mark if you want best STOL and best cruise set ur prop to 5800 at full throttle straight n level. It should give you around 5100/5200 in a 60knt climb. Ask Gary or Wal at Bert Flood. Gundy
Kyle Communications Posted June 2, 2012 Posted June 2, 2012 Thanks Gundy...I have the 72inch bolly not the std 68 inch that most have. I will adjust it at a degree at a time to get those specs
Gundy Posted June 3, 2012 Posted June 3, 2012 Yeh Mark those figures will work for that prop. It's the best for Cruise and STOL. You can fine tune it for either after like Bill he needs it a bit finer because of his strip and he's happy to rev a bit higher on cruise. You know what I mean. Gundy
Planechaser Posted June 3, 2012 Posted June 3, 2012 How do you find the MGL stuff....do you have any sort of EFIS in there or just the separate single digital gauges. I have been looking around at EFIS and the MGL stuff is very good pricing a fair bit cheaper than the rest Put in a diagram of the panel, Kyle. I havn't had any bother with the MGL stuff. It cost my about $260 over the standard stuff to have them put in. I find it much easier to process the raw number than a dial. I thought because I waould have a set of numbers in my head( Vne Vf Etc etc) That instead of decifering a dial or slide bar every time, much better just to see the number. The big 'ol ASI is a dream when doing low level technical stuff! Ditto the RPM and oil temp/press. I love seeing the number at a glance. I like the look of their EFIS gear. A bit of over-kill for my job but that dosn't stop me trying to convince myself every now and then. I've done 350 hrs/12 months flying so far and I can't fault them. Would find it ard to go back to Dials!!
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now