Silly Microlight question...

[davydine]

Hi,

This is probably a very silly question but it was brought to mind by Biggles and his arboreal antics and the inaccuracy of fuel sight guages

If I ever save enough to get my NPPL (JAR PPL not an option due to eyesight) then a three axis microlight could be a serious option.

If I were to fly a microlight with an empty weight of say 265 kg my weight plus passenger is, say, 160 kg that leaves 25kg for fuel.

How do you measure the weight of fuel on board, short of draining the tanks and putting in a precise amount? Or do you just take a best estimate and risk being slightly over weight?

Not sure how many forests there are for me to land on round here....

Thanks!

[flybymike]

Technically you will have kept a running log of the fuel quantities remaining based on hours flown from a given known point (tanks full)
Inevitably there is a degree of guesstimation involved.

[Andy H]

All the microlights I have flown have had some form of sight gauge, and those I have checked have been accurate to a litre or so. So knowing the weight of petrol (isn't it 0.72 kg / l ?) it is quite simple to calculate the weight of fuel on board surely.

Andy

[Jan Olieslagers]

All my instructors have assured me that the typical two-seater Rotax-powered ultralight is overweight anyway with two average weight persons on board, and more than the strictest minimum of fuel.

Edit further to Rans6Andrew's comment: this was meant to specifically mean 4-stroke Rotax.

[dublinpilot]

Instructors like to make general comments like that because they think it makes them sound knowledgable. There is little point in repeating them as they just become old wives tales.

If you want to know the facts, then look up the POH of the individual aircraft.

[rans6andrew]

the problem with microlights is that the designers/manufacturers have always squeezed the biggest (read heaviest) engine they can fit and still meet the rules of empty weight. The customers have then decided that the biggest engine is what they think they need.

In practice there are a fair number of aircraft about that do have some spare weight between the empty and MTOW figures. I have one myself. My Rans S6 weighs just 220 Kg empty, it is allowed to weigh 243 Kg. This gives me another 23 Kg of fuel/luggage in addition to the 15 Kg that is included in the empty weight permitted. In practice the tank cannot hold that much fuel so I can sneak a bit of luggage in as well.

By going easy on the pies I keep my weight in the 83 Kg (I am 6 ft 4!) range and my partner weighs in at less than that. This means that with a bit of careful packing we can take sufficient oil (2 stroke Rotax) and personal stuff for a touring holiday to France for 7-10 days and be just legal. By the time we come home, much of the oil is consumed and some duty free takes its place in the luggage rack.

If I was looking at buying a second hand microlight I would go along armed with an inspector and 3 sets of bathroom scales. I might take the scales along if I was looking for a new partner as well!

Rans6....

[Jan Olieslagers]

Andrew,
What you said about fitting the heaviest possible engine corresponds to my experiences. With a 2-stroke engine one would indeed have a bit of margin, and keeping the weight of the occupants within limits is a worthwhile exercise. OTOH 2-strokes have a certain reputation of becoming unreliable if not cared for very intensively - always seemed a bit feminine to me (ducking). I had my own grand moment of loosing power on take-off and toppling over less than a minute later behind a Rotax 2-stroke, it's hard to shake off bad memories.

And yes, certainly (bathroom) scales will have the final word to say vs. the POH.

One word of yours puzzles me, though: is there really such a thing as an "authorised empty weight" ?

[gasax]

I might be worth putting Jan's comment into perspective. Sur le continent the licensing arrangements for 'microlights' are very different to those in the UK.

The rigour with which we allow our rules seems well over the top. My aircraft a CH601xl is a microlight in many Europena countries - and yet mine - a lighter one weights 311kg. Obviously an aircraft like mine is going to be 'overweight' - certainly in terms of its legal category of 450 or 472kg.

Of course structurally it may well be perfectly OK - mine has a mauw of 560kg so although not legally a microlight it is perfectly safe structurally.

In the UK Section S has a maximum empty airframe weight and mandatory re-weighing so there is significantly more control.

And so are bourne many legends....

[Rod1]

If you go for the VLA version of a micro the running costs will be the same, but the useful load much better. On an MCR for example you get an increase of 50kg in your useful load!

Rod1

[patowalker]

Jan,

In the UK we have a maximum ZFW of 450kg, less 2 x 86kg occupants, less one hour of fuel at MCP. This means that most 912 powered microlights have a maximum empty weigh of 268 kg.

[flybymike]

I know bugger all about microlights but any regulation regime which requires pilots and passengers to look like anorexics and carry only enough baggage to brush their teeth and only enough fuel for a single circuit is absolutely barmy.

[Whopity]

Or do you just take a best estimate and risk being slightly over weight?In doing so you also risk invalidating the permit the insurance and your livelyhood!
but any regulation regime which requires pilots and passengers to look like anorexics and carry only enough baggage to brush their teeth and only enough fuel for a single circuit is absolutely barmy.
The UK microlight definition was originally 340 Kgs and was a weight below which, regulation did not apply! In order to improve undercarriage and braking systems the weight was raised to 450Kgs which then resulted in better, higher performance aircraft, rather than the proposed modifications.

[J.A.F.O.]

What you must remember is that good British air is far more complicated than that filthy foreign air and therefore needs to be treated with more respect. That is why we have different rules in the UK, sometimes I wish we had simple air like they have in most of the rest of the world.

They haven't built a microlight yet in which I wouldn't have to either leave the passenger behind or the fuel and luggage. Ah well.

[flyingflea]

The reality is that on a modern microlight (I owned a CT for 5 years) the MTOW was seldom an issue. True with 2 adults the maths is very simple from memory - CAA limited 450KG max and 268KG max empty leaves very little for fuel. The CT however can take 130 litres of fuel which would put it way over weight with 2 up.

The CT however is a great performer and can safely (but illegally in UK) take 2 adults and a lot of fuel. Its more a regulation issue than performance as the same aircraft can legally fly at a much higher MTOW in other countries.

[flybymike]

Insurance remains the bugbear. I suspect that the earlier blanket assertion that "all microlights are operated overweight" is probably true, and it is often argued that regulation which is ignored, is bad regulation. However this must offer the insurers a massive potential get out clause on a huge potential percentage of claims. One could even argue that this might be a case of insurers obtaining money under false pretences.

[VOD80]

Not trying to be a smart-ar5e, but are there any documented cases of insurance companies refusing to pay out after an accident?

[rans6andrew]

always carry a lighter, if you do have a mishap open the fuel drain and burn off the excess!

Or buy an aircraft with weight to spare.

Rans6...