Change in Max Wing Loading Rules

Air Worthiness Manual Chapter 549 has max wing loading limits that have been bothering me, my RV-8 would be classed as a "high performance aircraft" if I declared a gross weight above about 1810 lb. A "high performance aircraft" can only be flown by a pilot with a type rating for that aircraft. I wasn't looking forward to dealing with this.

But Friday, I finally took a closer look at the exemption to CAR 549.01, which effectively supersedes AWM 549. The max wing loading requirement has changed. Previously, the max allowable wing loading depended on wing area, flap area and maximum flap deflection. The exemption removes the complicated formula with flap area, etc, and now just has a hard limit of 20.4 lb/sq. ft for aircraft with flaps. This is great news, as it means I no longer have to deal with the hassle of obtaining an RV-8 type rating.

Declared gross

Hi Kevin,

I'm not sure where, but I seem to recall reading somewhere that unlike in the US (where the builder can declare with impunity whatever max gross they want), that in Canada the inspector will want some justification for declaring a higher gross than that of the designer. MD-RA inspectors are human, and thus subject to variability, so it may depend on who you get as to whether this would be an issue or not.

Kevin
The change was made in the last year as the previous formulae had no real basis on the difference that an airfoil can make.(IMHO) It must have been carried forward from the dawn of flight! Also the rules were not read the same way accross this country. The 20.4 lbs/square inch rule at least is consistant and can be solved with simple math.

java said:

I'm not sure where, but I seem to recall reading somewhere that unlike in the US (where the builder can declare with impunity whatever max gross they want), that in Canada the inspector will want some justification for declaring a higher gross than that of the designer. MD-RA inspectors are human, and thus subject to variability, so it may depend on who you get as to whether this would be an issue or not.

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Yeah, I've heard that too. But, they have no regulatory leg to stand on. According to the wording in the exemption to CAR 549.01:

(3) Prior to issuance of a flight authority, an amateur-built aircraft shall be inspected in
accordance with a schedule acceptable to the Minister:
a) for workmanship and general serviceability;
b) to detect apparent and obvious unsafe features; and
c) to provide reasonable confidence of safe operation.

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I wonder what justification they expect for the gross weight of a one-of design? If they are difficult, I am quite confident that I could get a ruling from TC to clarify things, as the guys who wrote the regs for amateur-built aircraft work one floor below me. I haven't discussed this specific issue with them, but I have a pretty good handle on their approach. They are very careful to not apply a too heavy regulatory hand to this class of aircraft.

Obviously the laws of physics still apply, no matter what gross weight the builder declares, so people have to be prepared to operate the aircraft differently if they are above Van's recommended weights. I've done some basic wing bending moment calculations, and have come up with load factor vs gross weight limits that will ensure that the wing bending moment remains less than it would be at 6g at the recommended aerobatic weight. Also, I will only operate from smooth, hard-surfaced runways if the weight is above 1800 lb. I'm also pondering a day only limitation for landings above 1800 lb, to reduce the probability of a hard landing. Maybe also a lower cross wind limit.

Wing Loading

A hard figure of 20.4 Lb Sq/ft would just be too simple. I read it is the lesser of a "hard formula" or 20.4 lb sq/ft. I have not worked this out as yet and hope the 20.4 applies.
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(b) For Use with Imperial Units (fps), the lesser of:

W/S = 13.3 + (0.96 x (Rfs) x (Rfc) x (df)) lb/ft2; or

W/S = 20.4 lb/ft2.

George in Langley BC said:

A hard figure of 20.4 Lb Sq/ft would just be too simple. I read it is the lesser of a "hard formula" or 20.4 lb sq/ft. I have not worked this out as yet and hope the 20.4 applies.
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(b) For Use with Imperial Units (fps), the lesser of:

W/S = 13.3 + (0.96 x (Rfs) x (Rfc) x (df)) lb/ft2; or

W/S = 20.4 lb/ft2.

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George - I don't know why TC has to make it so confusing, but the stuff you quote is what you see if you look at the supposed official CARs. But, it was all superseded by an exemption that was signed on 30 Aug 2006. The exemption is hidden away here. The part on wing loading is in para (40), and it says:

(40) Amateur-built aeroplanes without flaps, having a wing-loading exceeding 65 kg/m2 (13.3 lb/ft2), or with flaps, having a wing loading exceeding 100 kg/m2 (20.4 lb/ft2), are classified as high performance aeroplanes.

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That wonderful complicated formula with flap area and flap angle is history.

Retraction

You are right Kevin, I just read the exemption and see that I did make a mistake. I was going to see if I could delete my last post but your reply beat me too it.