It's a worry: shrinking Savannah XL specifications

[eightyknots]

I received my December 2010 copy of Kitplanes magazine from the USA which contains the 2011 kitplanes directory. Something didn't quite look right when I looked at the Savannah XL (known there as the Savannah VGW [W for wide] in North America).

 

I decided to compare this with the 2010 kitplanes directory found in the December 2009 issue. As you can see from the attached photo, the cruising speed has shrunk by a whopping 10 knots, which is almost 19 km/h! The new cruising speed is now about the same as the Zenith CH-701. I wonder what happened?

 

Another spec that shrunk as well was the build time which reduced from 350 hours to 250: again, you wonder what has changed during the past twelve months for this to occur? :raise_eyebrow:

 

It was nice to see one figure which increased: the number of XLs "completed and flown" went up by 125 which indicates that a newly completed Savannah XL joins the fleet every three days.

 

 

 

[Spin]

A dose of reality maybe? I haven't flown one of the newer generation Savannahs, but I'm always a bit cautious of figures that are noticeably out of line with the competition, ie a stall speed of 30mph suggests that there is a fair wing area and a relatively high lift aerofoil, neither of which are conducive to a high cruise. Bitter experience suggests that there is no such thing as a free lunch . I'd be interested to hear what local owner's experience is - the aircraft is on my shortlist for when I eventually buy an RA type. Of course it is also possible that someone put a mix of mph and kts figures into the directory.

 

This same discussion raged after one of our members flew a fairly speedy Aussie design and was prepared to accept a claimed stall speed in the low 20's at face value. Maybe I'm just getting old; but faith is a wonderful thing in it's place, that place isn't aviation and technology however. There are accepted methods of measuring the various performance parameters and I get a wee bit narky when manufacturers deviate from them when publishing performance data, quite possibly for commercial reasons.

 

 

[HEON]

It is a great pity that aircraft specifications seem to be written by politicians and used car salesmen.

 

Now some are design specifications that often do not happen in the real life but I can see why there is a reluctance to change to the real world as some potential purchasers think the difference of 5kg of payload or 2kt of speed are a dealbreaker.

 

Thus we have range figures such as for one European LSA quoted at 4000rpm with Rotax 100hp, or other same engine high strut braced fixed wing aircraft aircraft with a number of other drag features quoting a cruse speed of 110kt...in a dive from 10000ft? All figures seem to be subject to "fudging"...I even now use a tape to check L, W, and H.

 

As an importer I am not isolated from this however if you care to view my web site or current mag adds you will see a few changes to the factory (design) specifications based on actual W&B's and flying the aircraft.

 

If it sounds too good remember it probably is

 

 

[eightyknots]

A matter of trusting the manufacturer :-|

 

A dose of reality maybe? I haven't flown one of the newer generation Savannahs, but I'm always a bit cautious of figures that are noticeably out of line with the competition

I did a comparison between a close competitor of the Savannah between the 2010 and 2011 kitplane directories, namely the Zenith CH-701. It has had a shrinkage in cruise speed from 98 knots down to 90 knots. Other Zenith aircraft kept the cruise speed the same. It is, as you say Spin, probably a reality check that did this.

 

The problem I have, if anyone is going to 'invest' serious money in an aircraft, you would like to be properly guided by the specifications furnished by the manufacturer. It's simply a matter of trust, as far as I am concerned.

 

 

[rankamateur]

Did anyone consider the childishly simple typographical error, or would we all prefer to have a witch hunt?

 

 

[Guest Maj Millard]

Eightyknots, Don't worry about the cruise on the Savannah, I flew one from Casino to Townsville in 9hrs airtime, which is about the same as I would have done it comfortably in my slicked up 912 100hp standard Lightwing.

 

Cruise-speed in anything is objective anyway, and is affected by many factors on a given day such as :tailwind, headwind, turbulance etc, etc.

 

Even the big-money slicked up jobs often have to reduce power, and speed, due to turbulance, and often have to do so quicker because of their small thin wings, with high wing-loadings aand corresponding rough ride.

 

The Savanah VG does a surprisingly great job at cruise with it's high-lift wing, and really is a mockery to many more expensive machines available today..Ultralighting has never been about blinding speed anyway, if you want to go fast, buy a jet. Most recreational pilots prefer to take time to enjoy the trip, the experience, and the view ! ........................................................................Maj...

 

 

 

 

 

 

[Spin]

Geez, someone must have featured on Santa's naughty list:laugh:

 

Maj I'm still none the wiser, what TAS did you get on your Savannah flight, I've no idea what your Lightwing cruises at.

 

 

[Ultralights]

cruise speeds can vary between different aircraft of the same type, our savvy cruises in still air at 87 Kts indicated at 5100 rpm or 70 kts in rough air, though other savvys will cruise a little faster at 90 kts, due to being built a little lighter, or smaller tyres, or different prop type or pitch, with full fuel and baggage to MTOW our cruise speed will drop by about 4 or 5 kts.

 

there are many variables that can effect actual cruise speeds

 

 

[Spin]

Thanks Ultralights, from what I've heard, your's sounds like a good example so with some allowance for tyre size etc 90kts seems like a realistic claim. Pretty good I reckon, esp when you consider what the lower end of the speed range looks like.

 

Are you guys still on for a run up north? Wx apparently due to give us a bit of a break around Thurs.

 

 

[Ultralights]

sadly we are still rained in down here, and the forecast for the trip north is not looking like improving any time soon unfortunately, at the moment we are just waiting to see what happens. though the weather down south looks clear, so might do our first trip to Victoria, who knows..

 

 

[Guest Andys@coffs]

So it had to be marketing fluff given that fuel capacity and range did not change but speed did! In truth if there was a fundamental change in cruising speed then range must change as well.

 

Andy

 

 

[Guest Maj Millard]

Spin, Sorry I wrote a longer post but then lost it, so that was my shorter one. When I quote cruise-speed I use average ground-speed, per the GPS, which is what matters anyway when going cross-country.

 

You always use best economic cruise RPMs, which vary a bit between aircraft with the same engine. In the Lightwing and Savvy VG I'm usually between 4800-5000 for a good fuel burn.

 

You can push it faster of course, but no point getting there 30 minutes earlier, if you run out of fuel with the airport in sight !.

 

In my Lightwing I am generally happy if I can maintain mid 80s in cruise. Occasionally it'll whip up to low 90s, which I take as cream. It is a big training wing after-all. If there is a good headwind, I have to be content to just stay in the high 70s.

 

On one leg home from Shute harbor to Townsville, the GPS sat on 99kts all the way !. This ****ed me off after an hour, so I bumped up the rpms 200 and she whipped up to about 104. I have done what I can on my Lightwing to slick it up a bit.

 

The Savvy VG with the same engine and similiar prop (3 blade Kool Prop), showed similiar numbers as I recall, except that with the Savvy you had to reduce a bit, and slow down more ofter in turbulance, with the high-lift wing due to the rough ride. The Lightwing wasn't so affected. The operating speed range on the Savvy is very impressive though, and something the big fast stuff can't, and won't match, especially the over the fence speed.

 

My 912 100hp Lightwing spins a three-blade Powerfin prop, which I have pitched for cruise as that's where it spends most of it's time. I only turn about 5200 full power at take off, but still gets 800-1000FPM climb, fully loaded. My Savvy figures are for the standard VG.100hp, the XL or S may even be better.The Kool prop was pretty smooth and efficient, and the tundra tires didn't seem to impact cruise speed as much as expected, but are certainly worth having come landing time !...............................................Maj...

 

 

 

 

 

 

 

 

[Spin]

Thanks Maj, that is good gen, always like to know what real world figures are. I was only tweaking your tail anyway - I suspect the onset of cabin fever may explain things!

 

I recall the tongue in cheek explanation for Maules and KR2s always being slower than book figures, was that they suffered some sort of unusual aerodynamic interference when another aircraft was in the vicinity;)

 

 

[Guest Maj Millard]

Well said David.

 

Spin, Additionally I learnt some time back that it's never wise to believe a manufacturers performance figures !. There is more than often a natural fudge factor.

 

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...

 

 

 

 

 

[dazza 38]

The Sting Carbon from what i have read.Is a A/c that has to "get on the step", for cruise.I read this in a flying article.Never had the oportunity to fly one myself.

 

 

[coolair]

2010 Savannah VGW builder

 

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]

The Savanah VG does a surprisingly great job at cruise with it's high-lift wing, and really is a mockery to many more expensive machines available today..Ultralighting has never been about blinding speed anyway, if you want to go fast buy a jet. Most recreational pilots prefer to take time to enjoy the trip, the experience, and the view ! ........................................................................Maj...

Maj, as you can see from my rec flying 'name', I am pretty happy to fly slow (and low): eighty knots will be just fine for me :big_grin: .

 

You posted some really nice pictures on this thread! One that seemed a bit worrying though was you flying above what looked like pretty solid cloud cover. But, as you posted those pictures on here, you must have found the hole to descend through. Which island is that a picture of?

 

 

[Guest Kevin the Penniless]

Witch Hunt! Witch Hunt!

 

 

[flightygirl]

nothing wrong with slow, we just arrived at Ballina, from wollongong, indicating 85 kts all the way at 5100 rpm, and ground speeds varying from 75 to 110 Kts! no higher than 1500 ft... as for approach speeds, anywhere from 60 kts no flap, 45 to 50 kts with 1 stage of flap to 35 with full flap.

 

as for actual stall speed with full flap, thats a bit harder to define as the position error of the Pitot tube at such high AOA it can read 30ish, usually 27 to 28 in a pretty level stall, but can read 0 kts if the nose is high.

 

the "step"" comes at about 80 kts, you can cruse at 80 kts with 5100 rpm all day,nose reasonably level, but if you give it a bit more, say to 5300 rpm, then the tail will lift, AOA will decrease and speed will increase to 90 kts, pull power back to 5100 and it will cruise at 85 to 87 at 5100 on the step so to speak. the higher speed at 85 creates more lift than 80, so the wing setlles on a lower AOA, hence the "step"feeling.

 

and i have seen 3 savannah VG wides in my travels so far, well, since April this year.

 

 

[dazza 38]

Hi Rach and Rob.Just to let you guys Know.If you leave Ballina and get stuck with weather on the Gold Coast, Hecks field or Murwillumba, you can always stay here.Ph- 0413200506

 

 

[dazza 38]

Thanks Flightygirl,That is completely consistent with a high lift STOL wing and what anyone should expect. That is my style of aircraft. I do prefer the tail wheel config of the AAK Hornet though, that's because I have tail wheel disease

David

Thats why i like flying the Savage Cruiser Cub.Low and slow. Nothing like popping open the door.61 knots and under. I fly over Moogerah Dam living the dream.1000 Feet or less.

Before anybody shoots me down in flames- It is approved in certain areas.It is Boonahs (Airsports) Southern Training area . Approved below 500 feet in some areas. If you have a LL endorsement or with a instructor.Cheers;)

 

 

[flightygirl]

Hi Rach and Rob.Just to let you guys Know.If you leave Ballina and get stuck with weather on the Gold Coast, Hecks field or Murwillumba, you can always stay here.Ph- 0413200506

thanks Dazza.

 

We are only going as far as Ballina this time round... just up here for work today... head back to sydney tomorrow then off to Orange next week. We think we might then head out west to wherever the wind takes us.

 

Will try for Qld another time when there is less water about.

 

Rach

 

 

[Guest Maj Millard]

Rach, Glad to hear you at least made it to Ballina, and good decision not coming North of the border right now...not real dry !! From the figures you mention it sounds like your Savvy goes quite well.

 

eightyknots, I'm not above solid cloud unless there is a quick (and visable) way down. Often it'll be solid one side, and broken on the other. The second cloud shot was an early morning departure during a ferry, with the sunrise coloring the cloud top. I've always liked that shot. The 'Island' is not an island but a cape. Cape Upstart on my regular commute from Townsville to Shute Harbour. We do have lots of Islands up and down the coast, and the photos below are of real Islands.

 

 

 

 

 

 

[eightyknots]

Rach, Glad to hear you at least made it to Ballina, and good decision not coming North of the border right now...not real dry !! From the figures you mention it sounds like your Savvy goes quite well.The second cloud shot was an early morning departure during a ferry, with the sunrise coloring the cloud top. I've always liked that shot. The 'Island' is not an island but a cape. Cape Upstart on my regular commute from Townsville to Shute Harbour. We do have lots of Islands up and down the coast, and the photos below are of real Islands...

It's an absolutely beautiful part of the country and the pictures show this well.

 

 

[frank marriott]

I find the best way to refer to the cruise speed of different aircraft is by using the TAS - GS speed is generated by weather. TAS for a particular power setting gives the reader the speed to be expected - modified by wind for GS.

 

Geneally speaking speeds quoted in GS, kph, mph are used by people selling aircraft and trying to imply a higher speed then

 

achievable.

 

Frank