MTOW confusion

[Guest Rocko]

Hi all

 

This might sound like a ignorant question, but it still seems pretty strange that we can have a single identical aircraft, with several MTOW figures.

 

I understand many aircraft have weight limits taken from foreign requirements, such as the 450kg European MTOW. I understand we have a MTOW for amateur build of 544kg, and yet the manufacturer can also have yet another MTOW which is the structural MTOW, or that used for GA registration, which could be anything else.

 

My Hanuman was a classic example. It is rated in Europe to 450kg, in Australia to 544, and the factory provided information it can be flown to 550kg safely.

 

I understand the manufacturer of a 450kg aircraft has probably done significant testing to rate it to this, for their overseas registration. I'd also imagine they have done significant testing to determine the ultimate strength of the aircraft, to allow them to be flown at 544kg (or whatever) as homebuilt safely.

 

So, without going into ages old history of the RAA, why can a home built aircraft (with a 544kg MTOW) be any safer, or any different, than a factory built aircraft (say, with a 450kg MTOW). And, lets face it, if it IS exactly the same aircraft, why is it any less safe to fly a 450kg MTOW aircraft to 544kg, if it can be readily registered as this too?? You have to consider that the factory built aircraft is probably the safer of the two, so should be able to handle the higher loading.

 

Seems to be a double standard there somewhere. But it seems to put a lot of very nice second-hand factory built aircraft at a serious disadvantage, when it comes to selling them.

 

 

[Mathew Ker]

I should think the other temptation is for people to become complacent about weight restrictions at all. Sure we know there are weight limitations, but it's not hard to imagine someone thinking, "If it can fly at 450kg, but is also legal at 544kg, but I heard that the factory says it will safely fly at 550kg, surely it will take 600kg!" Before long this same person might not consider any weights when loading the aircraft and this will end in tears when they fly a different aircraft; or the met conditions are differnt; or any number of scenarios.

 

I guess anything which is rated to perform at a certain level must have a 'safety margin' built in to it - this goes for flying or any other rating. The critical thing would seem to be having the discipline and common sense to work within the safety margins you are licenced to operate in.

 

This will never illiminate the human element of course! :hittinghead:

 

Safe flying, Mathew

 

 

[ab0767]

It is my understanding - and correct me if I am wrong, the actual aircraft has a MTOW of 550kg. The rules we fly under (RAA) state the MTOW is 544kg, this has nothing to do with the plane it is just a figure that was made up when RAA negotiated with CASA. Likewise in Europe, they negotiated the figure of 450kg.

 

 

[Guest Redair]

Good question Rocko, I thought I understood all this MTOW stuff, but after reading these postings, I am starting to have second thoughts. If the RAA limit is 544, and has nothing to do with the plane... does this mean we could fly something with a MTOW of 3 or 4 times that, but as long as it never actually got past 544 it would still be OK to fly it? (Seems doubtful to me) However, how is it possible to have these LSA jobbies with MTOWs of 600, and use them under RAA rules? Re-reading the Ops Manual, has servered to further confuse me. I think I'll just stick to flying my kite, I know that is at its limit when there is no more string left!

 

Redair.

 

 

[ab0767]

The MTOW for the LSA category (different set of rules) is 600kg, everything else is 544kg max

 

 

[Yenn]

It is legal to fly a plane with a MAUW of above 544kg as a registered RAAus plane, but at no more than 544kg. This is how a Murphy Rebel can be RAAus registered.

 

The other way to legally fly at above 544kg in RAAus is to fly a homebuilt amphibian which has a slightly higher weight allowed.

 

In short if you want to fly RAAus you will have to keep the weight down to the legal limit regardless of the manufacturers MAUW.

 

 

[Guest brentc]

544 is the limit for an RA-Aus aircraft operating under 95.55 rules and regs (seaplanes can be higher)

 

600 kg's in the maxumum for an RA-Aus aircraft operating under LSA guidelines.

 

Some aircraft are limited to 450 kg's, such as Ian's Millenium Master, because of certifiction requirements for Europe which didn't / don't allow higher than 450 kg's, even though it may be capable of even 700 kg's.

 

Kit built aircraft that don't need to comply with certain regulations can then be flown at the higher aircraft design weight, rather than the certified weight.

 

Whilst it would be easy to say that you could buy an aircraft that weighed 600 kg's MTOW and register it under 95.55 but only carry the pilot and fuel, however this can't necessarily be done because if you refer to the technical manual, there's a formula in there that determines if you can actually do this legally.

 

 

[Guest Rocko]

So, basically, there is no way of changing registration type to increase the allowed MTOW? I know little of the various requirements apart from 19. However, I did see somewhere on a post where a GA registered aircraft was converted to RAA rego, then converted back to GA, who would only accept it as experimental, which I assume has a different MTOW. What stops a person changing the rego on a factory built aircraft with a 450mtow, to something with a 544kg, and remove the advantages factory built have? Or isn't it possible?

 

I'm not trying to circumvent rules set out by the RAA or anything, but if someone is prepared to forgo the benefits of the factory built category, to an "experimental" class, then wouldn't the rules chance accordingly?

 

 

[Guest Rocko]

I should point out, the post I read, which now I can't find, wasn't using the change in rego to circumvent MTOW requirements. It was something about a factory built GA aircraft, converted to RAA. Guy sold it, saying it could be reregistered either RAA or GA, but GA could only be done as "experimental", with consequent issues from this.

 

 

[Guest babs1aus]

Mtow

 

Well it is all prety clear in the opps manuals, the formulas the weight limits, etc as are the specs and limitations put on designs both certified and kits by the manufacturers or designers. How ever there appears to be a trend of people maybe not so much fudging but using the formulae in the manual to register a type, being fully aware that they are going to load their plane far beyond its capacity. Im not saying that these aircraft arnt capable of the weights they are loaded to. However when you see a monstorous looking plane with 2 1oo kg plus pilots and 80 to 100 litres of fuel on board plus some luggage. Something does not compute try the maths out.

 

 

[Guest disperse]

You have the TRUE MTOW. which is the Engineered true capabilities of the aircraft.

 

I could buy a mcr 4s with a engineered MTOW of 750kgs. And is a 4 seater.

 

I then remove the back seats and register under LSA, and only because of the registration I chose the legal MTOW is now 600kg. But the plane is still capable of carrying 750kg safely.

 

My other option is to take the same exact plane . Put the back seats back in, and register as GA. now my legal MTOW is back up to 750kg

 

so it's not the true MTOW (the true abilities of the design) but it's the LEGAL MTOW.

 

just like a truck. It may be capable of pulling 90 tons but can only legally loaded to 42.5 ton

 

 

[TechMan]

I then remove the back seats and register under LSA, and only because of the registration I chose the legal MTOW is now 600kg. But the plane is still capable of carrying 750kg safely.

My other option is to take the same exact plane . Put the back seats back in, and register as GA. now my legal MTOW is back up to 750kg

You will have a problem there as no manfucturer will sign out a statement of compliance under LSA for a 4 seater (with the rear seats removed).

 

If and once you register the aircraft LSA however, you cannot re-register it as VH Experimental.

 

The aircraft will remain as LSA, as the manufacturer has signed it out as being such.

 

Once a duck, always a duck.

 

Chris

 

 

[Big Kev]

:black_eye:

 

Sorry to dredge this up again guys, but I consider I understand mtow from both perspectives, but am still confused.........

 

My scenarios are: I am looking for an aircraft. A number fit my bill, but not my legs and weight (198cm, 130kg). With half tank must have 70kg spare.

 

1. VP-2 re-engined with 582. Empty 250- 260kg, manuf. mtow 1040lb (473kg). Payload 223kg, possibly allowing a cut lunch.

 

2. Lightwing 582 has same payload as 912, with different mtow. I believe there are some differences for engine accomm. Some happily advertise that the mtow is 544kg.

 

3. GT500, 582 mtow 1000lb, 912 1240(?), 582 being advertised to me @ 560kg.

 

When I looked at the figures initially, I thought 'great, light aircraft, 544 mtow'. Being the safety concious type, I would go by the manuf mtow, but this also concerns me somewhat, as the J160 I flew last year must have been close to overload- and this also brings into question the aircraft available for RAA training, in the Canberra region.

 

The above sounds a bit disjointed on re-read, but my point/ question is: you can't just bump up the mtow to a para's max (ie gt500 582 and GR582 to 544kg)?

 

Still confused.

 

Cheers

 

Big Kev

 

 

[Guest pelorus32]

Try this:

 

1. Each aircraft has a design weight. This is the weight that it is designed and tested to. With RAAus aircraft the maximum is probably the CS-VLA rule limit of 750kg. Many are designed to a lesser weight. This is the weight that the aircraft cannot exceed even if the regulations allow it to;
    
    
   
2. Regulatory limits. These are the limits that various countries place on aircraft. In Australia the two main ones are the 95.55 limit of 544kg and the LSA limit of 600kg. As others have pointed out there are for instance German limits of 450kg;
    
    
   
3. Certification limit. It is possible that an aircraft is designed to a weight - say 750kg - but then approved in an overseas category at the maximum regulatory weight for that overseas country - say 450kg. Then when the manufacturer applies for 95.55 para 1.6 approval in Australia they have to rely on the overseas approval so the aircraft is only approved here at 450kg even though it is designed to 750kg and the regs would otherwise allow 544kg. This is a limitation bought about by the certification requirements.
    
    
   
4. Then there are the sea plane allowances as others have pointed out.
    
    
   

 

 

 

Hope this helps.

 

Regards

 

Mike

 

 

[Guest basscheffers]

My scenarios are: I am looking for an aircraft. A number fit my bill, but not my legs and weight (198cm, 130kg). With half tank must have 70kg spare.

Not cheap, but an LSA registered CTSW would probably fit the bill. Even gives you full fuel.

I am 1.92/115, so not quite as big as you, and the Sportstar fits me just fine. Mine is only 544KG (company says 550), which fits me, full fuel (65 liters, 4 hours) and 80KG pax. Newer ones go up to 575 and 600 respectively.

 

How on earth did you fit in a J160!? :confused:

 

 

[jetjr]

Stall speed sometimes drives variable MTOW

 

No one seems to have mentioned stall speed. 45 kts is the limit for RAA. And this also drives MTOW for both LSA and others. RAA chose 544kgs and manufacturers made A/C to suit

 

ie J200 - aircraft is rated to 700kg BUT this is at 49kts stall, it can only meet RAA stall speed at 544kg

 

So in summary in GA it can be 700kg but under RAA is restricted to 544kg. There are plenty of others including Lightning etc etc

 

Some (like the lightning) can stall beneath 45kts with higher load so will be able to take advantage of the increased weight limit unlike J200

 

JR

 

 

[Big Kev]

:confused:

 

Stall is something I hadn't considered.

 

I looked up the 160 after I wrote last night, they have a payload of 240, but a max fuel load of 95! And we have the photos of our 40 deg day in Tocumwal, also the Sportstar which I didn't get to try on (not really interested- too expensive).

 

The above also relates back to what I wrote- it may be ok for the 160 to max out at 544, but do the others for sale (which don't have J numbers or specs listed) which are listed, for instance, as 'Jabiru 2.2' or such, have the same mtow?

 

I can see myself with a low time C150 at this rate........

 

Cheers

 

Big Kev

 

 

[Guest basscheffers]

I can see myself with a low time C150 at this rate........

Useful load on that one is only 220KG. Leaves about 20KG for fuel with your requirements! Besides, would you fit in one? They are tiny!

There new heavier aircraft possibly coming to RA-Aus, are just that: heavier. Most 544KG aircraft, let alone the 600KG LSAs, have better useful load.

 

Piper Tomahawk, also to be had for reasonable prices, have better useful load than a 150/152. If you are are willing to go all out GA, there's loads of old Warriors and 172s, etc. which will work, being 4 seaters and all. (for small 1960s people, so 2.5 seaters for the rest of us)

 

 

[Ross]

The original Jabirus were originally supplied with 1600 cc motors and were eventually upgraded to heavier 2200 cc motors manufactured by Jabiru. The new factory built ones then had impressive climb performance with the 2200 motor.

 

Any old Jabirus with the 1600 cc motor that were converted to the 2200 motor would need at least a new weigh and balance besides a different cowl and probably propeller etc. It would have still needed to comply with its original MTOW and as I understand it and also be loaded to comply with a max stall take off speed of 45 knots in the landing configuration.

 

It seems to me that all advertisements for Jabiru aircraft should specify the actual model of the aeroplane with its serial number and the engine model number and its serial number.

 

A Jabiru advertised as Jabiru 2.2 could be an old LSA 55, UL-D,J120c, J160, J160c, J170, J170c and number of others. Each one of the above aircraft has a very different performance and a different load capacity and even different again depending on their options and the limitations caused by the pressure height of the aerodrome and the type and length of airstrip.

 

The Jabiru web site has a chart explaining the difference for some of the models and some more explanation in the text for others including the factory built J-120c.

 

There is also some explanation of the different rules of the various registration schemes.

 

 

[Stewart J]

Hi Big Kev,

 

Not sure what type of 'craft you're after, but if you're considering doing any building yourself, then you may want to check out Australian Aircraft Kits, all metal fully enclosed ultralight aircraft kits They offer an all metal STOL Hornet. Its MTOW is 6ookg, making it LSA reg. Don't know if that's a problem or not. One of the links there is to Alan Sattler progress and the bloke sitting in the part finished 'plane is 6'8" (2.03) and he looks pretty comfy.

 

Hope this is of some help,

 

Cheers, Stewart

 

 

[bushpilot]

To add to the MTOW confusion, consider this recent advice from RAAus:

 

"There are 3 different versions of the J170. The first two are:

 

An ultralight up to J170C but the later Cs were different. The early Cs and below had a MTOW of 544Kg. The late model Cs and the Ds were LSA so their MTOW is 600kg. Lastly there is an amateur kit version with a MTOW of 544Kg

 

So if the aircraft is a LSA (it has a Certificate of Airworthiness in LSA) the MTOW is 600kg. The rest are 455kg.

 

This also applies to the 160 and 120."

 

 

[Guest ozzie]

gee i can see the odd head to head battle on the ramp between one of the new up coming casa dudes and some poor jab owner over whether it is a early or late c or d. x y z abc

 

 

[Guest burbles1]

The rest are 455kg. This also applies to the 160 and 120."

I'm sure that 455 kg should be 544kg - that is surely a typo. As for the 120 and 160, according to the official figures from Jabiru, they are limited to their design MTOW of 500kg and 540kg respectively.

I'm sure that RA-Aus will set the record straight If you ask them to clarify any confusion - it's really important no-one exceeds the MTOW, either with legal or design weight - the reputation of rec pilots and RA-Aus depends on it.

 

 

[Bill Hamilton]

---- odd head to head battle on the ramp between one of the new up coming casa dudes and some poor jab owner over whether it is a early or late c or d. x y z abc

Folks,

 

Thankfully, not much chance of that, given that a CASA AWI or FOI is very unlikely to have a clue about "community administered" aircraft ----- but they all understand low flying and similar misbehavior in any aeroplane.

 

Just to add a little complication, around the world there are a variety of stall speed limits for these kind of aircraft, JAR VLA being 37 kt, so Jabiru make one model that fits that criteria.

 

The "administrative" weights are more or less arbitrary, and prior to the "544 kg", the weight was 488kg for AUF. To clarify further, AUF did not "choose" 544. The LSA weight came with the package.

 

During the period of the PAP/CASA Review ( John Sharp was the Minister) the PAP decided that it was likely that quite a few aircraft were "probably" flying over 544 kg MTOW.

 

We agreed with the Canadian approach, neither Canadians, nor Australian come in SSB size (Standard Starving Biafran), and arbitrarily increased the weight to the same a the "new" Canadian weigh ---- hence 544. Why??? 544 ---- so that we could use the Canadian example as the "safety case" ---- and not have the weight change process strung out for years by local bureaucracy.

 

For different reasons, we also changed the stall speed limits, because it was the PAP view that very low stalling speeds made for serious controlability problems in quite moderate gusts common in Australia, during landing and takeoff.

 

The JAR/VLA limit of 37 kt was not accepted, and the result is what you have today. This really upset some of the "low momentum" purists, but we were of the view that it was better to not have the accident in the first place, rather than be able to step out of wreckage unscathed, because of the low speed ---- that V squared didn't getyah.

 

Very few "ultralights" (for want of a better word) or amateur built aircraft have been subjects to anything like the design analysis, let alone static and dynamic testing, of a CASR/FAR 23 aircraft, so be very careful about exceeding the design limits ----- as in don't.

 

Seemingly "identical" aircraft may well have subtle but vital production differences, depending on the design AUW for the intended registration category ---- do you know how many layers if glass there was in a layup ----

 

Another really good reason why is lack of accountability for "gust loading" ( not the gust on the ground that tips you on your wingtip) and it is fair to say that some designers allow for this by "over engineering" the static strength of the airframe.

 

Our Australia manufacturers serve us well in this regard, Jabiru is a good example, but not the only one.

 

I don't have the same faith in the "certification" of some of the LSA I have looked at.

 

Regards,

 

 

[bushpilot]

To add to the MTOW confusion, consider this recent advice from RAAus:"There are 3 different versions of the J170. The first two are:

 

An ultralight up to J170C but the later Cs were different. The early Cs and below had a MTOW of 544Kg. The late model Cs and the Ds were LSA so their MTOW is 600kg. Lastly there is an amateur kit version with a MTOW of 544Kg

 

So if the aircraft is a LSA (it has a Certificate of Airworthiness in LSA) the MTOW is 600kg. The rest are 455kg.

 

This also applies to the 160 and 120."

With latest clarification from RAAus it seems that the earlier advice (above) was incorrect.

 

Just because an aircraft is LSA doesn't necessarily mean its MTOW is 600Kg, it means it is under that number. To find the approved and certified MTOW - look in the POH (flight Manual) for each aircraft.

 

For Jabirus, it seems that the J160 is 544kgs MTOW in any category and LSA versions of J170 are 600kgs; same with J230. The J120, regardless of category, is 430 kg - same as the old ST models. If in doubt check with Jamie at Jabiru.