fallowdeer

Whenever there's a conversation about fuel burn vs RPM in a Rotax the very first thing to clarify is (assuming ground adjustable propellor) what the wide open throttle setting is. Without similar WOT settings then one engine at 5000RPM is likely to be producing very different amounts of power compared to another engine also at 5000. Those who (erroneously, and I have seen a few) have their 912 pitched WOT at 5200RPM will clearly be putting out more power at 5000 than someone who is at 5000 but who has WOT at 5800. As an exaggerated example compare fuel used in any engine under load and then fuel used at same RPM but no load. This is why power charts have RPM and manifold pressure. Peter

Let's cut to the chase, basic physics and thermodynamics. A 912ULS pitched to wide open throttle at 5800rpm is developing its rated 100hp. At 5000rpm, with the same pitch on the propellor its developing around 65% power, 65hp obviously. A very good guideline for brake specific fuel consumption for a carburetted petrol aero engine is around .45lb/hp/hr. Or about 272gm/kw/hr if you prefer. So it follows that to develop 65hp for an hour you'll use .45 x 65 equalling around 29.25lb of fuel, 4.0 imperial gallons or so. If you like it in metric the numbers are 272gm x 49kw = 13.3kg, or 18 litres or so. Even if your engine is 10% more efficient in terms of BSFC then you'll still be burning around 15/16 litres per hour. While a particular 100hp 912 may be burning 12 or 13 litres per hour at a constant cruise setting then rest assured the power output is commensurately low. If I'm just mucking around in my 100hp Savannah, low power settings and lots of idle time yes my fuel burn is down in those sorts of ranges. But if I'm cruising at 5000rpm ( My prop is pitched to WOT is around 5700) then yes I burn in that range of 17/18litres per hour on a trip. There is no magic. Peter

There is about 75 metres between the edges of the parallel vectors.

The most relevant fact of all is that it seems that the aircraft was not landed on a recognised vector. There is a grass vector parallel to the sealed runway, obviously with a space between. It appears that the aircraft was landed in between the grass vector and the sealed runway.

Well I'll bite. No because a propellor is not a screw boring through the air. It's a wing creating lift. Think of a yacht, a well designed and trimmed sail can sail way faster than the wind speed.

kgwilson. I know you've qualified your post by saying "this century" but Sioux City deserves to be mentioned in any discussion of uncontained failures. Peter

Following this thread from over the ditch I'm truly impressed by how complicated your regulator has managed to make the management of recreational aviation. We only have two classes of microlight aircraft, Class One and Class Two with the primary difference being one or two seats. Any maintenance in the not for hire or reward microlight world can be done by any person (avionics and static system certification perhaps being an exception) with the proviso being the annual inspection which requires a LAME or Inspection Authority. An IA is an authority granted to an individual by the controlling Part 149 organisation. It doesn't require a formal aircraft engineering qualification but obviously does require a certain depth of knowledge and experience. It'd be interesting to calculate whether this more liberal regime has created a greater accident rate from maintenance failings. Personally I doubt it. And if it flies, no matter what it is or whether it's lifted by hot air or rotor blades or whatever or built by Joe Bob or Boeing it carries a ZK prefix. Seems a lot simpler over here.... Peter

One of the overlooked advantages of the 912 is that an FAR 33 fully certificated version is available, the 912S. I'm not sure there is much difference in reality between the 912 S and the "uncertificated" version, the 912 ULS. Perhaps "undocumented" might be a better term. I reckon the parts would most likely come from the same bin and the extra cost is amortising the certification cost, and perhaps some extra parts testing. I'm sure the 915 will also eventually appear, if not already, in both versions. So in my opinion a 912ULS is as close as you can get to the standards of a certificated engine without it actually technically being one. Peter

Hi John M Close, in the Ruamahanga near Papawai. Yep, 305kg plus another 30kg of fuel plus me equals about 420kg. Peter

Aero Classic 21/800 on the mains and 600x6 Condor nosewheel. Run the mains at minimum pressure that they don't rotate on the rims.

I always thought All Up Weight was technically the total weight of airframe, fuel, crew, load etc at any point in time. Often used interchangeably (if in error) with Maximum Takeoff Weight.

Agree with carrod01 don't want be reminded of the ones I usually work with about 2m long, black with a big zip.....

PA38 in 1979. $33/ hr solo $36 dual. My little brown envelope pay packet had about $120 in it each week. PA28/180 was $48/hr.

Yep, OAT and dew point are what I keep an eye on when considering carb icing. And of course OAT necessary for density altitude calculations. Peter

Hi Lyndon In conditions conducive to carburettor icing my suggestion would be to use the alternate warm air supply to maintain 20-24 degrees air box temperature. This is in line with the ICP Savannah VG flight manual. (Available online, Google it) Compared with traditional carburettor heat systems on Lycoming and Continental engines there appears to be less of a performance loss when using alternate air. For this reason in the wintertime I put a small (about 5mm) sleeve around the control wire between the knob and panel, thus keeping a partial supply of warm air at all times. This results in the air box temperature mostly staying in the range I want. As an aside a very experienced commercial helicopter pilot I know used to, when operating a R44 with carbureted engine, always flew with a trickle of carb heat on except when he needed maximum power. Peter

Yes

Hi Lyndon If you ever fly in places/conditions that are conducive to carburettor ice the simple answer is yes, it is worth installing the sensor to monitor air box temperature. Don't believe those who will say that Bing carburettors are immune to icing. Perhaps they are somewhat less susceptible than other types of carburettors but it can still happen My viewpoint is from personal experience, and experiences of one or two other pilots personally known to me. Peter

Hi Bob Yep will contact him. Well thanks again for yesterday. I flew this am, couldn't help myself...mountains and sloping paddocks... Then washed the plane, was pretty dirty. Helped Dave H with something on his plane then a Foxbat taxiied up to the hangar. Was Tony ZK-BIC from down south and another guy who had just bought the Foxbat and they were ferrying it from Taupo. So gave them my car to go into town and then home for me and more cataloging parts.....up to around 600 now..... Intend lining the box in black polythene. Peter

Hi Mark I'm highly impressed with your building ignition modules; dread the day when I have to replace one of mine. I like the idea of retrofitting the "soft start" feature, are you building that in. I'd hunted around a bit for one of the aftermarket Bullyhawk ones but they stopped making those a long time ago. Peter

The wing loading and stall speeds of a Metroliner III (SA 227) and a Beech 1900D are very similar; I don't think the F104 comparison is too valid.

The CAA will in time publish the he results of their enquiries into this event. Even though this aircraft does not appear to have been registered as a microlight we are fortunate here that the CAA devote the same effort into investigating fatal microlight crashes as they do GA ones. All their reports are online, as are those crashes and events that are elevated to TAIC (Transport Accident Investigation Commission) scrutiny.

Now show us some pics of a few back country strips!! Peter

My VG stalls clean power off at 30knts and dirty power off 26knts, speeds verified as much as possible by GPS. Comes with a little buffet that is so close to the stall that it isn't really useful as a warning then a left wing drop. For what it's worth the aircraft is very well rigged and flies hands off well. I've practised stalling the aeroplane with partial power but personally I'd be wary of intentionally stalling the plane with full flaps and full power. I don't subscribe to the theory heard from time to time about such and such an airframe never stalling and just "mushing" down at a very high rate of descent. A canard configuration maybe where the canard obviously stall first before it yank the wing up into a high enough AOA, given a slow even entry that is. Given sufficient elevator authority I'd think most wings can be pulled up to their critical AOA, and we haven't even got anywhere near discussing accelerated stalls. The rub is though that in my opinion the way we practise and get used to this sort of stalling behaviour is very artificial and doesn't relate well to what is actually happening in incidents where stall/spin is a factor. I'd wager that just about every pilot who has stalled/spun in was perfectly competent in recognising, and recovering from, an incipient stall resulting from an intentional entry in balanced flight on a steady heading. What I do really like about my own aircraft's behaviour down slow is that at flare at 28knts or less power off I still have a ton of elevator authority to raise the nose. The previous owner installed VGs on the underside of the elevator and swore by the improvement they generated here, they only come "into play" so to speak as the elevator reaches considerable deflection. I haven't flown a "standard" VG to see if there is any difference. I do know however that this is the flight regime that some very experienced CH701 pilots bend their aircraft, slowed right up high AOA and power off. Maybe more to do with those grippy slats letting go. A bit like caning a WRX or similar on a hard surface, all good and maximum grip but when they let go they let go I think it's a safe bet that most stall/spin accidents (apart from the metre too high round out type) don't start from straight and level. I try to remind myself of this ever time I'm taking off or landing from a steep hill strip or manoeuvring at low level. Draw your own conclusions. Peter

Yep would be sure nice to be a wee bit faster. Mate in next door hangar has recently completed a Glasair III. We worked out he gets about the same MPG as the Savannah. Of course the IO-540 uses three times the fuel. But he goes three times faster. I was out trundling along at 75knts one day when he called me up and he did a 230knt fly past. I can imagine now what it would have been like in WWII flying a Swordfish or similar, seeing a couple of FW190s flash past and pull up and waiting for them to swoop past on another pass..... Peter

Ha. Who cares about the bump over the air box. After all what part of a Savannah VG is pretty?????? Except for the performance that is STOLing it into some tiny patch of hillside or riverbed or whatever is pretty fun.... Peter