Sling 4 Around the World

[pieter001]

Mags, stop typing and go fly the SLING 4 and let me know what you think

[Mags]

Morning Guys
I went yesterday to the airplane factory and was privileged enough to take the Sling4 for a flight with a test pilot.I realy wanted to do this to compare the sling 4 with the sling 2.I have flown my sling 2 now for 155 hours and having the same engine as the sling 4 i thought it would be a good comparison.
Getting the ok from Mike we took off and 250 meters down the runway at 50knots we got airborne.
It definitely felt that there was more lift and bigger wings.Other than that no difference in performance.This was without the turbo boost.
We got to altitude and decided to do some stall tests .First we did it without flaps and got to the stall with a little shudder at 48 knots.With some rudder inputs we kept the wings level and she literally just sank down with no wing drops or anything funny.With full flaps the stall was at 39 knots and with a little power getting her back to 43 knots we could do a 360 degree turn with the wings at 30 degrees.Absolutely stable.
Trying to work out the best glide speed we went up 7500 feet over Walkerville and cut the power.We then decided to see if we can make it back to Tedderfield on the glide.We both had our doubts and were very surprised when we made it with plenty room to spare.Gliding at 63 knots descending at about 400 feet a minute.The landing was a non event as it is all the same as the sling2.
After landing at Tedderfield the discussion turned too speeds and Mike was adamant that the sling 4 would be faster than the sling2.This was obviously his new baby and he would say that.I on the other hand thought bigger means more drag and in good South African spirit the race date was set for this morning.
Getting next to each other in the air, settings went up 115% and it was balls to the walls,and low and behold he sat next to me and even got a meter or two on me.We pulled it back to a 100% power and i might have gotten a meter or two on him.I was really impressed.The sling 4 obviously perform as well as the sling 2 and i can just say thumbs up to Mike and the team.

Michiel

[WillemGouws]

Hi Michiel

Thanks for the feedback, what is your cruising block speed on your 115HP Sling? (assuming that will be more or less the same for the 4 seater)

[Mags]

Hi Willem

On average 112 knots indicated at 75% power 19l per hour fuel burn.

Michiel

[PJL]

PS - Thanks for your 2c worth PJL - I'll test out precisely that on the next flight. The standard Airmaster prop uses Warp Drive blades and has a 70 inch diameter I think. Ours has a 72 inch diameter (ie - we've go the slightly extra length one). Hopefully that''ll also make things a little more efficient.

James I am so pleased that you have fitted the 72 inch blades!!!! I bought the 70 inch with the kit but I found that it was not performing the way I felt it should and replaced it with the 72 inch blades and I am now very happy with the improved cruise performance +- 115mph in the Kitfox.

PJL

[pieter001]

Nice write up Mags You are perfectly positioned to give a good overview as your SLING 2 also has the 914 Rotax and you've put a lot of hours on it. Thanks for sharing your impressions with us, invaluable!

I've been dying to get some understanding of flight performance and obviously a good deal of planning went into the SLING 4... Induced drag seems to have been reduced, probably with the incidence, but this seems to only be noticeable at TOP speed so we'll not benefit in the cruise, but the overall performance is fantastic if you take the wing is 80cm longer and the fus 45cm, so a job well done by TAF!!

The round the world trip will likely give us a lot of interesing characteristic and handling info, as 230hrs surely is sufficient testing and tuning time. Can't wait to get the feedback.

This is exciting information and it is great to have a light 4 seater which seems to be proving itself more than capable with 115hp and it will also carry a good load... need I mention again proudly SA

TAF, well done Trust the orders will come flying in! Can we maybe see a 900kg MUAW

[GL]

TAF, well done Trust the orders will come flying in! Can we maybe see a 900kg MUAW

I flew the Sling 4 this evening and can confirm everything mags said.

I believe they are planning on a MAUW of 850 kg which if a typical empty weight is 450 kg gives 400 kg useful load = 80kg + 80 kg pilots plus 60 + 50 pax + 30 kg bags plus 140 l fuel = 7 hrs.

And it climbs at 600 fpm at 850 kg so could easily go to 900 or even 1000.

[John Miller]

I recall Mike saying they weighed it empty at 472kg If that is so, then it leaves 278kg for the cabin if full fuel is carried (37 US gallons).

The Sling 4's natural competitor is the Dyn Aero MCR 4S, which I see has a 363kg carrying capacity with full fuel of 32 gallons.

The Dyn Aero manages 130 knots. Interesting comparison - I wonder how the new four-place Tecnam will stack up when it appears.

[GL]

The Sling 4's natural competitor is the Dyn Aero MCR 4S, which I see has a 363kg carrying capacity with full fuel of 32 gallons.

They may be natural competitors book what is the price of the Dyn Aero - The Sling 4 is R1m plus VAT.

Also S4 comes with the 20 kg ballistic parachute as standard

[John Miller]

Sling 4 will definitely be cheaper. Late MCR4S serial number 131 is on the market with very low hours (under 75 SN) for 1.2 bar including BRS chute and full glass panel. These are essentially A to B cruisers so cabin comfort is important and I doubt most occupants will want to be in either type for much more than a couple of hours.

[pieter001]

I'm way stupid on this topic, but what aspects (naturally safety and undercarriage strength) are considered when deciding on a MAUW?

It is my opinion that the SLING 4 with it's longer wing, can easily manage a 900kg load and will still boast good climbspeed. The undercarriage can be strengthened I'm sure, so why not go for 900kg and make is a VERY usefull 4 seater?

CG certainly comes into play... but that too I'm sure one can influence with a few arrangements of the componentry...

To me it seems like such a waste to throw away 50kg usefull and limiting this bird to 850kg, when I'm 100% confident that she has more than enough ability to safely carry 900kg and still have great performance and from what I read in Mags' write up, even a great glide I'm sure.

[GlennW]

I wonder how the new four-place Tecnam will stack up when it appears.

The Tecnam looks great too. Fitted with a 180hp Lycoming. It will be interesting to see the comparisons.

[heisan]

I'm way stupid on this topic, but what aspects (naturally safety and undercarriage strength) are considered when deciding on a MAUW?

It is my opinion that the SLING 4 with it's longer wing, can easily manage a 900kg load and will still boast good climbspeed. The undercarriage can be strengthened I'm sure, so why not go for 900kg and make is a VERY usefull 4 seater?

CG certainly comes into play... but that too I'm sure one can influence with a few arrangements of the componentry...

To me it seems like such a waste to throw away 50kg usefull and limiting this bird to 850kg, when I'm 100% confident that she has more than enough ability to safely carry 900kg and still have great performance and from what I read in Mags' write up, even a great glide I'm sure.

Often the determining factor is the wing strength. I think the lowest acceptable +G limit is 3.8G (for utility category aircraft). The wing must be demontrated to have an ultimate strength at least 1.5x this. So the wing must be able to support 1.5*3.8*MAUW. So to increase the MAUW by 50kg, the wing has to be strong enough to support and extra 285kg.

[pieter001]

thank you Heisan, good to know this.

The Sling 2 has a +6G limit, so I think the Sling 4 with its 80cm longer wing should not be too far off...

The round the world trip will provide valuable info. I'm certain that they'll be way over 900kg on many of the longer trips: 360kg fuel + 140kg pilots gives you 500kg and the empty weight of 472kg means that they'll likely be around 1000kg on TO. I'm also sure that the Sling 4 will behave very predictably and soundly with this weight, but let us wait and hear what the verdicts are when they are on their trip.

I still believe the Sling 4 will be done justice at 900kg and not 850kg.

[heisan]

thank you Heisan, good to know this.

The Sling 2 has a +6G limit, so I think the Sling 4 with its 80cm longer wing should not be too far off...

The round the world trip will provide valuable info. I'm certain that they'll be way over 900kg on many of the longer trips: 360kg fuel + 140kg pilots gives you 500kg and the empty weight of 472kg means that they'll likely be around 1000kg on TO. I'm also sure that the Sling 4 will behave very predictably and soundly with this weight, but let us wait and hear what the verdicts are when they are on their trip.

I still believe the Sling 4 will be done justice at 900kg and not 850kg.

The +6G limit will probably be ultimate load, so design load will be 4G, in which case, it may just be a paperwork excercise to reduce this to 3.8G, which would up the structural limit on MAUW to 894kg. There are also some performance requirements to consider, but maybe they will up the MAUW sometime?

Long range flights and ferry flights are done under a special permit, and are operated significanly below the accepted structural safety margins.