Weight limits in Canada

[Kevin Horton]

Pete asked a question in the Flight Test Forum that really doesn't belong there, so I'm starting a new thread here to answer it. He said:

Originally Posted by Mustang

Kevin,
I'm building an RV-8 also. I was perusing your site the other day when I found your POH. I downloaded it, and then I noticed that you had increased the max T/O wt. to 1900 from 1800. I pondered this and wondered if maybe the MOT would have something to say about it. Obviously you have though this through so I wondered if you could elucidate on this point a little for the unwashed.

Thanks, Pete

Pete,

I decided to look into a higher declared gross weight as I will have a heavyish aircraft. I've got an RV-8, with IO-360-A1B6, Hartzell prop and an IFR panel. Van's RV-8A demonstrator, with a similar engine and prop, and a VFR panel, has an empty weight of 1127 lb (Ref CAFE APR on the RV-8A). The RV-8 is reputed to be heavier than the -8A, due to those heavy gear legs, and the landing gear boxes. I've also got a Christen inverted oil system and an IFR panel. So, I'm guessing my aircraft will be around 1140-1150 lb empty. I weigh about 210 with flying gear, and I've got a good friend who weighs a fair bit more than I do. Add full fuel for a cross country, a travelling tool kit, etc, and the 1800 lb gross weight just won't cut it.

You raise an interesting point on how Transport Canada may view my planned declared gross weight. There are several aspects that I will need to discuss with the MD-RA inspector. First, there is the question of structural strength. If I had designed the aircraft myself, I could declare any weight I wanted, without having to justify it, as Airworthiness Manual Chapter 549, Amateur-Built Aircraft does not require a structural substantiation. The mandatory inspections are supposed to be for "... workmanship and general serviceability ..." (AWM 549.19(a)). If the inspector goes beyond his official mandate to interogate me about the gross weight being higher than Van's recommendation, I'll explain how I've limited the load factor to ensure the wing bending moment is less than it would be at 6g at Van's recommended aerobatic gross weight. I'll also explain that I've limited operations above 1800 lb to smooth, hard surface runways. That should ensure that landing gear loads are less than they would be than from operations at 1800 lb on grass strips, which Van allows. The only area that I can't easily address is loads on the flaps, as there is nothing else I can limit to trade off against the higher gross weight. So, I'll pay particular attention to the flaps, flap pushrods, torque tube and flap actuator attachments when I do inspections.

I'll do flight testing to determine whether the normal CG limits are acceptable at 1900 lb.

There is one interesting aspect that is uniquely Canadian though - AWM 549.103 has wing loading limits. If the specified wing loading is exceeded, the aircraft is classified as a "high performance amateur-built aeroplane". There is a complicated formula for the max allowable wing loading, which uses flap span ratio, flap chord ratio and max flap angle. I measured my flaps, and I come up with a weight of 1808 lb. If the gross weight exceeds 1808 lb, then it jumps into the high performance class. Cracking the threshold for "high performance" has licensing issues. The fact that the aircraft will be classified as high performance means I'll need to get a Type Rating for the RV-8. This should be a very entertaining trip around the Transport Canada bureaucracy, as no such type rating currently exists. I'll have to ask the manufacturer (i.e. me) to give me some ground training, and I'll need to conduct a "qualifying flight", whatever that is. I suspect I'll end up using an 1808 lb gross weight for some time, while the bureaucracy sorts out how to deal with the rules they wrote. I'll post the results on my web site, whenever I get to the end of the process.

Note: the threshold of 1808 lb is based on the following data:

Wing span of 23 ft (Van's data)
Wing area of 110 sq ft (Van's data)
Flap span of 57.5 inches (measured)
Flap chord of 11.25 inches (measured)
Flap travel of 40 degrees (Van's data)
The above data is with the traditional Hoerner style wing tips.

Newer aircraft have different shape wing tips, which gives a span of 24 ft and a wing area of 116 sq ft (both numbers from Van's). A gross weight of 1888 lb or higher would make it a high performance aircraft.

[Mustang]

Kevin!

Geez, that was some reply. Thank you very much for spending the time. Perhaps I will attempt to register mine at 1850 then, just to be on the safe side of the regs. ( I have the new style wing tips.) Which could be an option for you also if you get hassled.

I gotta go right now but I'll write more tomorrow about this.

Cheers, Pete

[Kevin Horton]

Back in January I mentioned a uniquely Canadian regulatory issue revolving around wing loading and weight limits. I fired an e-mail off to the TC guy in charge of this stuff, and finally heard back from him last week.

The amateur-built regs in Canada specify a maximum wing loading (see AWM 549.103) - if the aircraft's wing loading is too high, then it is classified as a high performance amateur-built aircraft, and that triggers a requirement that any pilot hold an individual type rating for that aircraft. The hoops you need to jump through to get an individual type rating are aimed at type-certificated aircraft, as they require ground training, etc. They need to be liberally interpreted to allow the square-peg amateur built aircraft to fit in the round regulatory hole.

CAR Standard 421.40 lays out knowledge, experience and skill requirements that must be met to obtain an Individual Type Rating for a High Performance Aeroplane. The experience requirement is easy to meet, as it is only 200 hours total time on all aircraft types. The knowledge requirement is a bit more difficult, as it calls for ground training on the aircraft type. But, this is only a standard, not a regulation, so there is a bit of room for interpretation. My friendly TC guy recognizes that a formal RV-8 ground school does not exist, so I simply need to convince him that I know everything I need to know about the aircraft. Given that I built it, that won't be too difficult. The skill requirement is met by my friendly TC guy climbing in the back and giving me a check ride. I suspect many TC inspectors would not feel comfortable climbing in an amateur-built aircraft, but I am lucky that this guy has an open mind.

My plan is to initially declare a gross weight of 1800 lb. After the flight test phase is complete, and I can carry passengers, I will do a check ride, obtain the individual type rating for an RV-8 then file the paperwork to increase the gross weight.

I suspect that many Canadian amateur-built aircraft owners are either ignorant of the wing loading regulation, or are ignoring it. Aircraft like Harmon Rockets, some Lancairs, etc probably have declared gross weights that require the pilot have an individual type rating, but I bet many of the pilots don't have one. They may think they have slipped on past TC, but their insurer could have the last laugh, as this would give them an easy reason to deny payment if there was ever an accident.

[flyboy1963]

Hey Kevin,
have you read about what Todd Bartrim...in Prince George did?

http://www3.telus.net/haywire/RV-9/C-FSTB.htm

He apparently registered his RV-9a at 2000 lbs or so....using the calculations you describe.
sounds like if you entertained the idea of some extended wingtips the area might help!?!?!

best of luck!

[Ralph Inkster]

I assume from the web page that Todd Bartrim has been flying for a few years.
MD-RA may have changed their policies since then regarding what gross weights they will approve (allow) during their inspections. My understanding is they will only approve what is specified by the kit designer, in our case Vans Aircraft.
They suggest if you wish to increase the gross weight, you would have to approach Transport Canada to modify your CofA for your desired weight, accompanied with documentation supporting your reasoning. This would have to be done after you have your permanent CofA (after your flight test period of course).
You should ask your MD-RA inspector if this policy is also the case for the import inspection.

Additional, the calculation MD-RA is now using in their final inspections for max gross weight is the one listed in 549 - NOT the calculation in the inspection guide on the MD-RA website (they are slightly different). On a final inspection we had done a couple months ago, the paperwork was kicked back because of this and we had to wait an additional 3 weeks for the flight authority to come...

[vlittle]

Hey Rob.

A couple of things to remember when you are specifying your gross weight:

Van's does not differentiate between gross weight with aft vs fwd c of g. If you compute the moments, an aft c of g will allow you to carry more weight without additional wing loading because it reduces the tail downforce.

In other words, carrying extra baggage may be ok when you do the computation.

The other thing is gear loading. My 9A gear is identical to the 7A gear which is spec'd for 1800 lbs. Coupled with aft loading (above), I rated my aircraft for 1800 vs 1750 (designed) because I could prove the math worked.

I also generated a loading envelope (like a Cherokee) that specified max gross vs c of g position.

When I submitted the paperwork, I ticked 'yes' in the aircraft modification box, with the reason 'increased gross weight'. That seemed to keep them happy.

I'd be interested to hear the current official MD-RA position on this. It's been a real problem for a long time.

V

[L.Adamson]

Originally Posted by Snowflake

There is an RV-7 here at my local field that I intend to look at more closely the next time he has his cowling off... I want to compare the sizes of the tubing in the landing gear structure and see if it is identical to the -6 gear or not. If it is, then the gear on the -6 should withstand the same loads as the gear on the -7.

Just FYI, since your's is a taildgragger...........the nose gear leg for the "A" models is the same for the 6/7/9's. Older 6A's used a 1" diameter, which was increased to 1.125" in the late 90's/2000 period. There was an SB for this change to the much stronger nose gear leg.

L.Adamson --- RV6A

[Kevin Horton]

The situation with maximum gross weights in Canada has changed significantly. Originally, we had the complicated formula in Airworthiness Manual Chapter 549 (AWM 549 - aka CAR Std 549) that calculated a maximum allowable wing loading as a function of flap angle, flap dimensions and wing dimensions. That was the formula I used to determine that if I had a gross weight greater than 1808 lb that I would need a an individual type rating to fly the aircraft.

Some time several years ago Transport Canada issued a wide ranging exemption to AWM 549. This exemption did many good things, one of which was to impose a much simpler max wing loading requirement. I think this exemption was actually first released before my original posting, but I wasn't aware of the existence of the exemption as it was well hidden. It has been reissued several times to extend the expiry date.

This exemption provides a max wing loading of 20.4 lb/ft^2 if the aircraft has flaps. For the RV-8, with the original wing tips like I have, the wing area is 110 ft^2. The max allowable gross weight is 2244 lb. If the gross weight is higher than that, it is considered a high performance aircraft, and you need to get an individual type rating.

I have not yet gone through the process to get approval for a higher gross weight. I have discussed the process with the local Transport Canada office, and I intend to work this issue while the aircraft is down for paint. I don't want to start the process until then, as I would need to give them the Special C of A while the file is reviewed, and I don't want to take the risk of the aircraft being grounded for a long period if they request more info.

[louis_special]

"Some time several years ago Transport Canada issued a wide ranging exemption to AWM 549. This exemption did many good things, one of which was to impose a much simpler max wing loading requirement."

Hi Kevin,
Just found the very informative thread on weight limits in Canada and your contributions in it, including the quote above which is very enlightening news for me. Any hint where I can locate the above referenced exemption?

I imported a hail damaged RV-6 (insurance write-off) for which I built all new horizontal control surfaces with .020" skins and a brand new horizontal stabilizer (the .016" skins were beyond repair due to hail damage). The MD-RA inspector imposed the 1600 lb limit at the importation inspection. When I calculated the lift area I found that I would still be under the lift limits at 1720 pounds with the C of G slightly towards the aft limits. Therefore, that is the weight I loaded the aircraft for my compulsory climb test. The aircraft climbed through 2000 ft during the 3 minutes with the power and airspeed at "enroute climb" settings.

August Lehmann
Built and flying Cyclone 180: C-GLEH
Rebuilt and flying RV-6: C-GAUG

[Kevin Horton]

Originally Posted by louis_special

"Some time several years ago Transport Canada issued a wide ranging exemption to AWM 549. This exemption did many good things, one of which was to impose a much simpler max wing loading requirement."

Hi Kevin,
Just found the very informative thread on weight limits in Canada and your contributions in it, including the quote above which is very enlightening news for me. Any hint where I can locate the above referenced exemption?

The exemption can now be found here. It covers a lot of subjects. The part about wing loading is in paragraphs (37) and (38).