Trying to find ways (STC's) to increase the maximum gross weight of a Cessna 172 above 2550#?
Or at least, to understand why such MGW increases are not available or approved in the USA?
Seems like such an STC would have widespread appeal for "the most popular airplane in the world"?
Specifically:
Why are Wing-X STOL kits not approved for the C172 in the USA, while other model Cessnas are?
The manufacturer has been claiming that FAA approval for the C172 is pending for many years . . . ?
If already installed on a Canadian C172, can it be imported back into the USA for re-registration?
Why did Cessna provide the C172RG for a 100# increase to 2650# MGW, but, not any fixed-gear models?
Many C172's have similar 180hp motors. Does the C172RG have "stronger" wings, fuselage, or landing gear?
Curious?
Dave
Cessna 172 Gross Weight Increases, or lack thereof?
Sun Feb 17, 2019 9:41 am
Sun Feb 17, 2019 12:02 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
Dave,
My limited knowledge of the mathematical side of aerodynamics is obvious, but I've been around bureaucracy many years. That gross weight, while very safe, has as much to to do with politics as safety is demonstrated by different gross in different countries and even states.
More can be carried by most if worked up to gradually. The wing on the Cessna Ag Wagon looks really good, but they are less popular than fatter, high lift, wings on most spray planes. Cessnas were faster than Pawnees and were most popular on government contracts putting out six ounces total volume per acre. Fuel limited load more than acreage.
What I appreciate about the Pawnee was its ability to jump a tree or wire and vibrate significantly without stalling, when too much overloaded. I was more careful with Cessnas. They don't shake before they stall.
Jim
My limited knowledge of the mathematical side of aerodynamics is obvious, but I've been around bureaucracy many years. That gross weight, while very safe, has as much to to do with politics as safety is demonstrated by different gross in different countries and even states.
More can be carried by most if worked up to gradually. The wing on the Cessna Ag Wagon looks really good, but they are less popular than fatter, high lift, wings on most spray planes. Cessnas were faster than Pawnees and were most popular on government contracts putting out six ounces total volume per acre. Fuel limited load more than acreage.
What I appreciate about the Pawnee was its ability to jump a tree or wire and vibrate significantly without stalling, when too much overloaded. I was more careful with Cessnas. They don't shake before they stall.
Jim
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Sun Feb 17, 2019 1:12 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
BluNosDav wrote:Many C172's have similar 180hp motors. Does the C172RG have "stronger" wings, fuselage, or landing gear?
I think the max gross weight set by the mfr is as much a constraint of safe performance limitations as it is structural.
Your question is good though.
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Sun Feb 17, 2019 1:45 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
170’s share the same problem and at an even smaller gross weight of 2200lbs. I can see it for the original 145hp versions, but with all the 180hp+ motors hanging off the firewalls now, there should be a gross weight increase available.
Sun Feb 17, 2019 2:37 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
Gross weight limitations are predicated on a number of parameters, and often have nothing to do with the structural robustness of the airframe. Probably the most common parameters have to do with performance, rather than concern over something breaking.
I spoke with Wing X folks about the getting the 170 and 172 kits approved in the US several years ago. They told me then that the biggest issue was FAA certification, and that the FAA at that time wouldn't consider any GW increase greater than (I think) 50 pounds. Since the kit adds some weight itself..... They told me at that time that they could see no point in proceeding with the certification in the US if that's all they could get, and that at the time they weren't pursuing a US approval. Maybe their attitude has changed by now.
And, if you were to purchase an airplane with the kit installed in Canada, then tried to bring it into the US, you'd have to remove the kit, and return the airplane to it's original configuration. That STC is not legal in the US, so no way you could import it.
As to similarities between the 172 and the 172 RG, note that the 172 RG was certified under the Cessna 175/Hawk XP/T-41 Type Certificate, NOT under the Cessna 172 TC.
MTV
I spoke with Wing X folks about the getting the 170 and 172 kits approved in the US several years ago. They told me then that the biggest issue was FAA certification, and that the FAA at that time wouldn't consider any GW increase greater than (I think) 50 pounds. Since the kit adds some weight itself..... They told me at that time that they could see no point in proceeding with the certification in the US if that's all they could get, and that at the time they weren't pursuing a US approval. Maybe their attitude has changed by now.
And, if you were to purchase an airplane with the kit installed in Canada, then tried to bring it into the US, you'd have to remove the kit, and return the airplane to it's original configuration. That STC is not legal in the US, so no way you could import it.
As to similarities between the 172 and the 172 RG, note that the 172 RG was certified under the Cessna 175/Hawk XP/T-41 Type Certificate, NOT under the Cessna 172 TC.
MTV
Sun Feb 17, 2019 3:46 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
mtv wrote:And, if you were to purchase an airplane with the kit installed in Canada, then tried to bring it into the US, you'd have to remove the kit, and return the airplane to it's original configuration. That STC is not legal in the US, so no way you could import it.
MTV
That is a shame. It's a good kit and really helps their STOL performance, from the ones I've seen fly.
Sun Feb 17, 2019 4:05 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
Interesting, my understanding was that for an aircraft being imported from the US in to Canada any modifications completed thru an approved FAA STC (not 337 or FA) would be permitted and issued a Canadian C of A, so much for regulatory reciprocity.
Sun Feb 17, 2019 4:21 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
Well, we name streets after the FAA in this country: “One Way”.
In any case, the airplane would have to be “Airworthy” by definition to receive a US A/W certificate and tail number.
Now a Canadian owner could fly that plane into the US legally....with Canadian registry and A/W.
Canada also has the “Owner Maintenance” category, also a no go in the US.
BUT, you want to talk “reciprocity”? When is Canada going to recognize Basic Med?
As they say in Quebec: Touché.
MTV
In any case, the airplane would have to be “Airworthy” by definition to receive a US A/W certificate and tail number.
Now a Canadian owner could fly that plane into the US legally....with Canadian registry and A/W.
Canada also has the “Owner Maintenance” category, also a no go in the US.
BUT, you want to talk “reciprocity”? When is Canada going to recognize Basic Med?
As they say in Quebec: Touché.
MTV
Sun Feb 17, 2019 5:05 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
mtv wrote:As they say in Quebec: Touché.
I believe it’s: Douché
Sun Feb 17, 2019 6:06 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
Here you go MTV, pretty basic really, maybe not identical but possibly better in some aspects,
Category 4 Certification
Canada Category 4. The only requirement needed to obtain this level of medical certification is a form of self-declaration similar to that of a driver’s licence. To that end, a screening medical questionnaire was created and the need to see a Civil Aviation Medical Examiner (CAME) eliminated. However, you need to have your family physician countersign the questionnaire if you want to carry a passenger on your aircraft. That’s right: no physical examination, unless of course you have or have had one of the conditions that we are concerned about, in which case you may need to see a CAME. So what can you do with a Category 4 medical certificate? You can fly day VFR, on a non-high-performance, four-seat or less single engine aircraft with a single passenger. In other words, if you are a light aircraft driver who doesn’t need or want to fly to the U.S. or IFR, you don’t need to visit your CAME. Unlike the U.S., it is possible to receive a Category 4 medical certificate if you have previously been denied a Category 1, 2 or 3 certificate assuming of course the medical condition has been dealt with and does not pose a flight safety hazard. You don’t need to have a driver’s licence and any decision made by Transport Canada (TC) can be appealed. The certificate can also be issued with a restriction as well, unlike the U.S. where you get it or you don’t, such as “no passenger” if your medical condition warrants.
Sorry for the thread drift, full reciprocity would be fantastic but highly unlikely it just makes to much "common sense" and regulatory agencies are loth to use that as a philosophy very often.
Category 4 Certification
Canada Category 4. The only requirement needed to obtain this level of medical certification is a form of self-declaration similar to that of a driver’s licence. To that end, a screening medical questionnaire was created and the need to see a Civil Aviation Medical Examiner (CAME) eliminated. However, you need to have your family physician countersign the questionnaire if you want to carry a passenger on your aircraft. That’s right: no physical examination, unless of course you have or have had one of the conditions that we are concerned about, in which case you may need to see a CAME. So what can you do with a Category 4 medical certificate? You can fly day VFR, on a non-high-performance, four-seat or less single engine aircraft with a single passenger. In other words, if you are a light aircraft driver who doesn’t need or want to fly to the U.S. or IFR, you don’t need to visit your CAME. Unlike the U.S., it is possible to receive a Category 4 medical certificate if you have previously been denied a Category 1, 2 or 3 certificate assuming of course the medical condition has been dealt with and does not pose a flight safety hazard. You don’t need to have a driver’s licence and any decision made by Transport Canada (TC) can be appealed. The certificate can also be issued with a restriction as well, unlike the U.S. where you get it or you don’t, such as “no passenger” if your medical condition warrants.
Sorry for the thread drift, full reciprocity would be fantastic but highly unlikely it just makes to much "common sense" and regulatory agencies are loth to use that as a philosophy very often.
Last edited by Mapleflt on Sun Feb 17, 2019 8:11 pm, edited 2 times in total.
Sun Feb 17, 2019 7:52 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
mtv wrote:Gross weight limitations are predicated on a number of parameters, and often have nothing to do with the structural robustness of the airframe. Probably the most common parameters have to do with performance, rather than concern over something breaking.
As to similarities between the 172 and the 172 RG, note that the 172 RG was certified under the Cessna 175/Hawk XP/T-41 Type Certificate, NOT under the Cessna 172 TC.
MTV
Thanx MTV. Performance may be the key factor? But, some types of performance enhancements seems to get better treatment from the FAA than others?
Perhaps RG's were able to demonstrate significantly better climb rates over obstacles on take-off (I'm skeptical about that**), or maybe somewhere else in the flight envelope?
Surprisingly, increased engine power doesn't get similar increases in MGW, since the XP @ 195hp and T-41 @ 210hp got nothing for their better performance. And I don't believe Stoots Aviation received any MGW increase from the FAA for their recent 210hp IO-390 STC? Wonder why?
Interestingly, in the C177 Cardinal series, when the Cardinal RG came along, it got a whopping 300# increase in MGW to 2800#! Was that because of it's (notoriously slow) retractable gear, or it's increase in horsepower from 180-to-200, or both?
** I find it hard to believe that more horse-power applied throughout the entire take-off roll & climbout, counts for less than a heavier & slowly retracting gear system that only helps after lift-off. And I always seem to be much-much higher than any obstacles, by the time that the gear is eventually "up and locked" in an RG.
Since better or bigger airfoils also increase performance, it would seem logical that Wing-X could demonstrate that in all models of Cessna? But, for some strange reason: there are models that get MGW increases, while others don't, yet, can be imported without a weight increase, and the poor C172 can't even get brought into the country! Weird?
It almost seems to come down to marketing? Cessna just gives away added MGW on their heavier RG's, in order to provide customers with the same useful load, and they have enough "influence" to push it through the FAA?
Last edited by BluNosDav on Mon Feb 18, 2019 1:01 am, edited 1 time in total.
Sun Feb 17, 2019 9:21 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
Blunose,
First, the Cessna 177 Cardinal is NOT on the same TC as the 175 series. Totally different airplane there.
You’re making a lot of “connections” that aren’t valid. For example, assuming that acquiring a gross weight increase via STC is a relatively simple matter. Changing an engine is tough enough to get done via STC, but increasing gross weight requires a whole additional level of flight test requirements. It can be done but it’s not a simple thing.
Again, gross weight can be limited by many different factors. Performance (including many parameters), things as basic as the landing gear and its attachments, and, yes, structures. There are a LOT of parameters. And, without knowing the specifics of all those models, it’s presumptious to make assumptions that these gross weight changes between models were done without testing and probably changes which may or may not be obvious.
An example is the GW increase on the Super Cub. Several outfits tried for years to get an STC to increase the Cubs gross weight, without success. Most gave up. Wipaire got it done, with some structural mods...and not terribly major. But they got it from 1750 to 2000. They did a LOT of testing, and I imagine it cost them dearly.
But, hey, if you study all the designs, do the engineering work, maybe you can get a gross weight increase for the 172 via an STC.
MTV
First, the Cessna 177 Cardinal is NOT on the same TC as the 175 series. Totally different airplane there.
You’re making a lot of “connections” that aren’t valid. For example, assuming that acquiring a gross weight increase via STC is a relatively simple matter. Changing an engine is tough enough to get done via STC, but increasing gross weight requires a whole additional level of flight test requirements. It can be done but it’s not a simple thing.
Again, gross weight can be limited by many different factors. Performance (including many parameters), things as basic as the landing gear and its attachments, and, yes, structures. There are a LOT of parameters. And, without knowing the specifics of all those models, it’s presumptious to make assumptions that these gross weight changes between models were done without testing and probably changes which may or may not be obvious.
An example is the GW increase on the Super Cub. Several outfits tried for years to get an STC to increase the Cubs gross weight, without success. Most gave up. Wipaire got it done, with some structural mods...and not terribly major. But they got it from 1750 to 2000. They did a LOT of testing, and I imagine it cost them dearly.
But, hey, if you study all the designs, do the engineering work, maybe you can get a gross weight increase for the 172 via an STC.
MTV
Sun Feb 17, 2019 10:55 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
-0-
Last edited by dogpilot on Thu Aug 06, 2020 1:09 am, edited 1 time in total.
Sun Feb 17, 2019 11:06 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
BluNosDav wrote:Cessna just gives away added MGW on their heavier RG's, in order to provide customers with the same useful load, and they have enough "influence" to push it through the FAA?
The Cutlass RG was 180hp if I recall. I flew one once and it was a nice airplane.
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Mon Feb 18, 2019 1:45 am
Re: Cessna 172 Gross Weight Increases, or lack thereof?
MTV,
You are correct that C177 Cardinals have their own Type Certificate, and I have edited that phase out of my post. But, my point remains:
that the trend within the C17X series of FG & RG airplanes appears "too perfect". The new RG's MGW just happened to go up, by the same number of pounds, as the new empty weight of the heavier RG, without any real changes being designed into the rest of the airplane? What a coincidence, that the engineered & tested performance of the RG's, just happened to increase perfectly & linearly for each & every pound of additional hardware that was bolted onto the new aircraft.
Anyway, Thanx Again! I'll go back to searching for a C18X airplane.
You are correct that C177 Cardinals have their own Type Certificate, and I have edited that phase out of my post. But, my point remains:
that the trend within the C17X series of FG & RG airplanes appears "too perfect". The new RG's MGW just happened to go up, by the same number of pounds, as the new empty weight of the heavier RG, without any real changes being designed into the rest of the airplane? What a coincidence, that the engineered & tested performance of the RG's, just happened to increase perfectly & linearly for each & every pound of additional hardware that was bolted onto the new aircraft.
Anyway, Thanx Again! I'll go back to searching for a C18X airplane.
Mon Feb 18, 2019 4:49 am
Re: Cessna 172 Gross Weight Increases, or lack thereof?
We had better not get started on this subject, it's a family show remember.......lets keeps this discussion "on point"
Cheers
Beer is cheaper in the US than it is in Canada, work on airplanes in the US.
Cheers
Mon Feb 18, 2019 11:06 pm
Re: Cessna 172 Gross Weight Increases, or lack thereof?
The kicker with the WingX STC is that it's a Candian STC on a US manufactured aircraft. And this is where the problem lies qith the 170 and 172 being approved in Canada and not the US. Oh regulatory fun... kind of like not being able to ship 406ELT batteries by air because they are lithium and this dangerous goods, and yet we require them to be in our airplanes...dogpilot wrote:BTW. if you read the bi-lateral agreement with Canada, I actually have, it is not a difficult document. If MOT approves something, such as an STC, it is valid here in USA. While you may find FAA FISDO heads that disagree, it is actually quite easy to prove them wrong. Just show them the agreement, its online. Almost all of them have NEVER read it or had anything to do with it.
Last time I went around the tree with the FAA was over airworthiness certificate issuance. The Atlanta MIDO office would not accept the wording on the certificate from Canada on a Twin Otter. Showed them the relevant excerpt from the Bi-Lateral agreement and they immediately backed off, "well not our responsibility so its valid, says so here!"
Now as to Canadian STC's issued on Canadian manufactured aircraft, they are valid overseas in other than US jurisdictions as well as USA. US STC's on Canadian manufactured aircraft are NOT valid in other than US or Canadian jurisdictions. STC's issued by jurisdictions other than the manufacturer's original jurisdiction are only valid in the country of issuance. So folks go get them nationalized in other countries, but it is by no means instant or guaranteed.
Issues of airworthiness are very different from licensing of pilots and AMT's. In Canada, want to work on an aircraft, you have to be endorsed for that specific aircraft or family of aircraft. You usually need to take a test. The bi-lateral only really covers issues of airworthiness and some aspects of pilot and AMT licensing. For example, I can't sign off work on a Canadian aircraft while in Canada, but I can while it is in the US. I can sign off a US aircraft in both Canada and the US. Beer is cheaper in the US than it is in Canada, work on airplanes in the US.
Tue Feb 19, 2019 4:59 am
Re: Cessna 172 Gross Weight Increases, or lack thereof?
It's always been my understanding that the intention of a bilateral is for exactly this reason. Therefore STC's or other TC/FAA approval processes would or should be recognized by both regulatory agencies. However its equally likely that the various floor level administrators of the "regulatory" agencies are equally unaware of the very existence of said bilateral agreement. Regulatory bureaucracy is destined to be the bane of GA flying, lets MFFA.
Tue Feb 19, 2019 8:48 am
Re: Cessna 172 Gross Weight Increases, or lack thereof?
If that were truly the case then we shouldn't have any problem accepting field approvals up here. Would be great but won't ever happen. If you read the bilateral agreement closely, it does talk about STCs developed in said country that holds the type certificate for said aircraft. Just studied a bunch on this with all my free time in AME school.Mapleflt wrote:It's always been my understanding that the intention of a bilateral is for exactly this reason. Therefore STC's or other TC/FAA approval processes would or should be recognized by both regulatory agencies. However its equally likely that the various floor level administrators of the "regulatory" agencies are equally unaware of the very existence of said bilateral agreement. Regulatory bureaucracy is destined to be the bane of GA flying, lets MFFA.
Tue Feb 19, 2019 8:58 am
Re: Cessna 172 Gross Weight Increases, or lack thereof?
-0-
Last edited by dogpilot on Thu Aug 06, 2020 1:10 am, edited 1 time in total.
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