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Max Gross Weight Increase, RV-6 Canada

H

H-Ottawa

Member
Hello everyone,

I posted a question in the regional CANADA forum section regarding the increase to Max Gross Weight for my RV-6...at 1600 lbs right now.

In Canada we have to go with what the kit manufacturer advertises.

I received the following from Transport Canada today and am wondering if anyone out there has any documentation from Vans that I could use as,
substantiating documentation"
i.e. Rv-6 with 160 HP, 180 HP, plans built vs kit built, etc....
Somewhere where it states that 1700, 1800 lbs is structurally acceptable...
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This is what I received from Transport Canada today:
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The process for application for Gross Weight Increase is as follows:

1. Make full and complete application which will include: Application for flight permit (TC form 24-0044) for purpose of conducting climb test, Fee payment for flight permit, provide TC with adequate substantiating documentation to justify a gross weight increase.

2. When Flight permit is issued, fly successful climb test and provide TC with satisfactory and complete Amateur Built Climb Test Report (TC form 24-0091).

3. Make application for issuance of new Flight Authority (TC form 24-0043) and pay fee for new flight authority.

4. Aircraft inspection by TC.

5. Relinquish superseded flight authority to TC.

All forms are easily accessible by simple Google search of the Transport Canada web page. I have included a link to all appropriate forms here: http://www.tc.gc.ca/eng/civilaviatio...-form-2943.htm

Fees also are readily available on-line in the CARS at CAR104 schedule VI and are as follows:
Issuance of a specific purpose flight permit, $45.
Approval of an amendment to the operations specifications set out in the flight authority?amateur built, $35.
You may pay these fees in person at the Ottawa TCC or by telephone at 1-800-305-2059.
NOTE: Inspector will require proof of fee payment for each application to be processed.

As far as substantiating documentation is concerned, we don?t have any conclusive list of expected items as all Amateur built aircraft are unique by their build standard. Citing that a similar aircraft on the registry have similar max gross weights is not acceptable as your build circumstances will not necessarily be consistent with those of the other similar aircraft. (i.e., the other aircraft may have heavier wing struts installed, etc.) It?s not like with Type Certified aircraft, where every aircraft of that type was built and is maintained to a consistent build standard.

With that, I would expect an applicant to provide loading calculations, weight and balance calculations that show aircraft in it?s current state (in any configuration) falls within the kit manufactures specified flight envelope.

Additionally, any modifications made to the structure of the aircraft in order to prepare the airframe to accommodate the extra weight and to what standard those mods were completed, with supporting documentation. Often, the kit manufacturer also has documentation specifying alternate max gross weights or other similar models/model upgrades that can be incorporated into the design and build of your aircraft to help substantiate your request.
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Happy Easter, everyone !

Harold
 
You are not the only one to fight this battle.

My suggestion is that you do the computations for max wing loading for non-aerobatic operations at your increased weight and show that it does not exceed the 1600 lb/6g aerobatic load.

Then, you should ensure that the landing gear is capable of the load. Confirm that it's the same gear and engine mount structure for the rv7 which has a higher gross. You may need to spec a maximum take off weight different than the max landing weight.

Finally, loading can help. If you carry weight in the baggage compartment, it reduces the tail downforce which must be supported by the wing. This can be computed and can help increase the max weight without increasing wing loading. What you get is a modified loading envelope where you can have baggage but not jumbo pax.

If any of this does not make sense to you, you can hire an engineer to make the calculations and use that as supporting documentation.
 
You might be surprised to know that sometimes GW increases can be approved based on the certification of similar aircraft. That was one of the factors which I used in upping the gross weight of my (non-RV) homebuilt. The civil aircraft registration database is a good source for this info.

Be prepared to have to go through the hoops of getting a special-purpose flight permit so you can do a climb test at the applied-for gross weight, and make sure you make the appropriate entry in the journey log BEFORE you do that flight test (this aircraft is operating under the auspices of a special purpose flight permit to allow flight test at xxxx lbs blah blah blah...). Also, sometimes it's easier to add human mass than ballast to the copilot seat - if you want to go this route, make sure you specify that you will have a flight test specialist in that seat to record data during the flight covered by the special purpose flight permit.
 
vlittle said:
You are not the only one to fight this battle.
My suggestion is that you do the computations for max wing loading for non-aerobatic operations at your increased weight and show that it does not exceed the 1600 lb/6g aerobatic load.
Click to expand...

Be careful. The 6g aerobatic load limit for the RV-6 is 1375#.
 
Mel said:
Be careful. The 6g aerobatic load limit for the RV-6 is 1375#.
Click to expand...
Also, note that it's not adequate to plot a line from 1375/6G (aerobatic) to 1600lb/4.4 (Utility) and then extend it to 1700 or 1800 at whatever G that works out to. If you don't understand why, as Vern suggests, hire an engineer to do the math for you.
 
Harold,

I went through this in 2010 to increase the gross weight of my RV-8 to 1900 lb. I sent the local TC office a letter stating:

Background ? Van?s Aircraft designed and tested the RV-8 for a gross weight of 1800 lb. The Van?s Aircraft prototypes typically are finished in a very spartan fashion, with minimal avionics and interior furnishings, and as such have empty weights lower than many customer completed aircraft. My aircraft has full IFR avionics, an aerobatic constant speed propeller with blade-root counter- weights, an inverted oil system, and other items that increase the empty weight approximately 75 lb higher than the empty weight of the prototype RV-8. A gross weight of 1800 lb is somewhat restrictive when carrying two people with full fuel and baggage.

Regulatory Requirements ? Neither CAR 549 nor Airworthiness Manual (AWM) Chapter 549 contain any design requirements relating to structural design. Thus the builder of an amateur-built aircraft has no regulatory obligation to make any engineering analysis or tests to substantiate that the structure is adequate to support the aircraft at gross weight. The only requirements relating to weight are AWM 549.103, 549.109 and 549.111. It is easily shown by analysis that the aircraft will meet the requirements of 549.103 and 549.109 at a gross weight of 1900 lb, using the wing area of 110 square feet and the engine power of 200 hp. The rate of climb will be slightly lower than it was at 1800 lb, but there was such a large margin to the requirement at 1800 lb that there is no doubt that the minimum climb rate requirement of AWM 549.111 will be met at 1900 lb gross weight. A confirmatory climb test will be conducted to document the performance meets AWM 549.111.

Engineering ? Even though there are no regulatory requirements to conduct a structural analysis, the laws of physics are still applicable to amateur-built aircraft. In the interest of living a long life, I have seriously considered the problem of a gross weight increase.

Wing structure ? The aircraft is designed for flight loads of 6g at an aerobatic gross weight of 1550 lb. Van?s Aircraft conducted wing static load testing that showed the wing exceeded the FAR 23 structural design criteria for aerobatic aircraft at this weight. I conducted a rudimentary wing bending analysis that showed that a load of approximately 4.75g at 1900 lb creates the same wing bending stresses as the 6g load that Van?s Aircraft recommends at 1550 lb. I will limit the load factors to 4.4g or less when the weight is above 1800 lb. Note that 4.4g is equivalent to utility category for an aircraft approved to FAR 23 requirements.

Landing Gear ? Van allows ops on unprepared runways, day or night, with full crosswind at 1800 lb. I will only operate from smooth, hard surface runways when the gross weight is greater than 1800 lb. Landings at weights greater than 1800 lb will be conducted in daylight only, and will be limited to crosswinds of 15 kt or less. These restrictions should ensure that the loads on the landing gear will be no higher than for operations at 1800 lb weight on unprepared surfaces.

Stability and Control ? I will conduct a full series of stability and control flight tests at a weight of 1900 lb and forward and aft CG before carrying passengers at weights above 1800 lb.

Performance ? I will conduct another climb test at 1900 lb weight, to confirm that the AWM 549.111 requirements are met.
Click to expand...
The local TC office approved my request for a gross weight increase.
 
Kevin,

Thanks for posting the letter and result. I assume once the flight tests results were confirmed positive, that a log book entry was made, the POH amended, and TC notified of the change and that is the end of story? Did I miss anything?

Bevan
 
Last edited:
My recollection is that you have to submit your Special C-of-A and they issue you a new one to replace it with the numbers updated. Unfortunately the turnaround time at TC for such changes is reportedly on the order of 2-3 months. Best to do this during the winter when you can afford the downtime.
 
Bevan said:
Kevin,

Thanks for posting the letter and result. I assume once the flight tests results were confirmed positive, that a log book entry was made, the POH amended, and TC notified of the change and that is the end of story? Did I miss anything?
Click to expand...

I thought I replied to this yesterday, but I must have missed hitting "Submit Reply" after checking the Preview. Oh well.

TC responded to my request for a weight increase by issuing a new Special Certificate of Airworthiness with the higher gross weight. I was legal to fly at the higher weight as soon as I had the new Special C-of-A in my possession. They didn't ask for a new climb report, so I didn't send them one - I think they bought my argument that the climb performance at 1800 lb was so far in excess of the minimum requirement that the climb rate would obviously still meet the requirements at 1900 lb. I did my planned flight testing at 1900 lb, then updated my POH. I did not carry passengers at gross weights above 1900 lb until I had completed my planned flight testing at forward and aft CG at 1900 lb - this was my own personal decision - TC did not require it.


Snowflake said:
My recollection is that you have to submit your Special C-of-A and they issue you a new one to replace it with the numbers updated. Unfortunately the turnaround time at TC for such changes is reportedly on the order of 2-3 months. Best to do this during the winter when you can afford the downtime.
Click to expand...
I returned my original Special C-of-A with the letter requesting the weight increase, so the aircraft was no longer flyable from that point onward. I did my weight increase while the aircraft was in the paint shop, knowing that it would be out of service for six to eight weeks. The local TC office took seven weeks to process the request.
 
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