Light Aircraft Association

I would like some thoughts and opinions please..
In appreciating that we have yet to hear the LAA IMC equipment requirements I have being doing electrical current draw calculations, prior to panel design, for my latest Rotax 912 engined build project. I am working on the assumption that a heated pitot is necessary for any flight in serious IMC and will be a definite LAA requirement.
In doing the above calculations I have come to the conclusion that equipping any Rotax 912 engined aircraft for IMC is going to be very hard if not impossible due to the constraints of the standard Rotax charging system.
A heated pitot( Garmin/Dynon) current draw at zero degrees C is 10amps only dropping back to 7amps at +40C.
The Rotax912 charging system.-quote from Rotax installation manual:-
18amps is maximum capacity at full power rpm
14amps is maximum continuous design load
Exceeding 14amps on a continuous basis will damage the stator.

Other things to take into consideration are, per display, say Dynon/Garmin glass panel 3.5amps draw per display or 5amps with backup battery, Strobes say 1.5amps + other necessary equipment, Comm/Tx , Flaps, Trims etc. Loading the aircraft with other stuff like VP prop, A/Pilot is a definite none starter it seems if a heated pitot is fitted.
I am aware that it is possible to fit an external alternator to the Rotax 912 but that is not straightforward and does open up another can of issues.

Thanks in anticipation.....

Interesting question Alan.
I would think the proposed specification will be based on CS23, which does require a heated pitot for IMC or 'Known Icing'.

Since there are quite a few external fits for alternators, was not aware that it was an issue, unless the vacuum pump gear drive was not fitted(or already in use with a vacuum pump).

The 912iS has two internal alternators, though it does seem difficult to get the ratings of them. Rotax quote:

The electrical power output of the engine was raised to 430 watt to provide for all modern avionics.

Which at 13.8v would be 31Amps as a rough guess. An external alternator can still be fitted at the rear.

From another site (http://www.experimentalaircraft.info) I found this.

A number of options can be installed: vacuum pump, alternator (the 912iS has a internal dual alternator 13 A for the ECU and 30 A for the aircraft), controllable propeller (some options can not be installed at the same time).

This is backed up the 912iS installation Manual which is protected.

Not a lot of good if you have already brought your engine

Hi Ian,

Thanks for the input however I already have a standard carburettor Rotax 912ULS engine for the project.

Alan.

Alan,
I think you need to find out if the 912ULS will be approved for night/IMC. My understanding is that the part traceability requirements will mean it has to be a 912S.
Donald

Donald,
We are pushing things off track but...
I could be confused here but as I understand it the 100hp 912ULS is the uncertified version of the 100hp 912S. I wouldn't have thought many/any LAA machines are using the certified engine.
The 912ul is the 80hp version.

Anyway, I have and are referring to in my question a 100hp Rotax 912 carb version uncertified engine which the majority of aircraft on the fleet are using.

The question though still stands, the fitment of a heated pitot in a IMC equipped Rotax 912 as currently fitted to the majority of the LAA fleet is virtually impossible as I see it when coupled with the other necessary instrumentation due to the constraints of the Rotax charging system. I just wonder if the LAA IMC steering group are aware?

Hi Alan,
Yes, I was wrong, it is the LSA types in the US that are equipped for IFR training (not legal for IFR operation) that have the certified 912S.

The manufacturers that offer these aircraft must have got around the electrical issues, because they claim to comply with FAR 91.205 and ASTM 2245 Annex 3 Additional Requirements for LSA Operated Under IFR.

The LAA requirements, of course, may be completely different, but the list of aircraft they consider suitable for IFR includes the Europa, Tecnam 2002 Sierra and MCR-01 Club, which are normally powered by the 912ULS.

Donald

Hi Donald,

Yes exactly. They have nominated these types as suitable( I assume airframewise) but I would hope consideration is being given to the fact that the Rotax charging system doesn't appear to me to be able to keep up with the necessary equipment requirements of flying in serious IMC.

I think most of these LSAs have external alternators as standard from the factory.

I think considering the list of aircraft published in the September magazine as 'suitable by the LAA for night/IFR' is to make the error of taking a small section of text out of context. The article clearly explains that each type has to be assessed, and the list is a very preliminary one of types that MAY pass that assessment as opposed to those not on the list that PROBABLY won’t. To date nothing has been given the green light, just the Bulldog has been approved to start trials. The type assessment and individual aircraft assessment protocols are yet to be finalised, as is the equipment fit, so to be deciding whether a particular aircraft or engine is going to be suitable or not simply isn't possible yet. It is frustrating for those who want to make decisions on equipment etc. but I'm afraid we'll just have to be patient for a while longer.

In the latest mag (Feb) engineering are quoted as having set a minimum wing loading of 60kg/sqmtr for IFR (page 29). This will I fear exclude a large number of Rotax powered aircraft.

About the same as a C150.

Forgive me for resurrecting an old thread, but I am particularly interested in this question, and was wondering if there is any update?

The specific question about electrical load analysis is important, but I was also concerned to know if the uncertified version (the ULS) is likely to be acceptable for IMC/night approval? The technical leaflet (TL2.28) is not entirely specific. It does say that powerplants must be of a certified type, but then it lists the Rotax 912/914 as acceptable, without specifically mentioning which version. Am I being too optimistic here? Should I just accept the "must be of a certified type" bit?

From TL2.28....

Section 1.2 – Powerplant Rules

1.2.1 The aircraft shall be fitted with a certified type
engine, meaning a type which is or has been
fitted to an aircraft holding a Certificate of
Airworthiness. In practice, for amateur-built
aircraft this will be either:
1. A Lycoming, or
2. An un-approved or cloned Lycoming
meeting the requirements of TL 3.15, or
3. A Continental, or
4. A Rotax 912/914 series, or
5. An alternative certified aero-engine

Hi holmesj

I had my Europa Tri-Gear approved for night and IMC last year. It has an non-certified Rotax 912ULS. I know of at least two other Rotax powered Europas going through the approval process at the moment.

All the best.
Carl
G-URMS

carlp101 wrote: ↑

Thu Jan 06, 2022 6:30 pm

I had my Europa Tri-Gear approved for night and IMC last year. It has an non-certified Rotax 912ULS. I know of at least two other Rotax powered Europas going through the approval process at the moment.

All the best.
Carl
G-URMS

Great news, thanks .