Don’t think you can increase the gross weight on an existing aircraft.This question is two-fold...
Are there any RV10 aircraft certified at 2900-3000 lbs?
Can an existing aircraft with a 2700 gross weight be re certified at a higher weight and what is the process?
Thanks in advance
Yep, the performance testing is one tiny facet of the whole picture. The more important part is the structure. Going over the recommended weight is reducing the engineering margin, the magnitude of which is information the average builder doesn't have.I know of several -10’s that were originally certified for over 2700 lbs. I believe the builders simply claimed they would be ‘in a condition for safe operation’, and supposedly would test them at the new higher weight during phase one. For an already flying airplane, you need to speak with a DAR. I *think* a new gross weight can be assigned, if you can convince the dar that it’s safe, and then go back to phase one and test it somehow. Clearly, just measuring the climb rate is not sufficient. 3000 lbs is >10% increase. I wouldn’t be casual about this.
Walt, where is the gross weight recorded for administrative purposes? I remember giving my DAR a sample W/B, but am unsure if/where that number was recorded for the FAA's records.Return to phase one for x hours and test at the increased gross weight, return to phase two after testing.
I don't believe the FAA has any record of WB/GW on an EAB, and they don't need to be involved if you decide to change it.Walt, where is the gross weight recorded for administrative purposes? I remember giving my DAR a sample W/B, but am unsure if/where that number was recorded for the FAA's records.
I own an amateur-built aircraft built by another person. That person was well aware that most loading scenarios put the aircraft dangerously close to its commonly-listed gross weight. When going through initial airworthiness certification he claimed an extra hundred pounds on the gross weight. When I asked him why he did this he explained the fear of being found overweight. After all, it only takes one pound over to be over...I don't believe the FAA has any record of WB/GW on an EAB, and they don't need to be involved if you decide to change it.
The OP asked if GW can be increased legally and the answer is yes, is it prudent, that's up to the builder.
Keep in mind one of the first things on an NTSB report is if the AC exceeded GW, by any amount. If you did, you're immediately at fault.
As far as I know, there is no regulatory binding gross weight limit for amateur built experimental aircraft. The airworthiness requirements are contained in the operating limitations, which are requried to be in the aircraft for flight. No gross weight limit is in that document, at least for my aircraft.Are there any RV10 aircraft certified at 2900-3000 lbs?
Can an existing aircraft with a 2700 gross weight be re certified at a higher weight and what is the process?
A small point, but still to be noted: you are reducing margin until you have burned fuel, expended ordnance, thrown baggage overboard or ejected unruly passengers sufficient to bring the aircraft back into the 2700 pound MTOW/gross weight limit. After that, you're good. For most RV-10's, that happens at about 60-80 pounds per hour in cruise, much faster in climb.As far as I know, there is no regulatory binding gross weight limit for amateur built experimental aircraft. The airworthiness requirements are contained in the operating limitations, which are requried to be in the aircraft for flight. No gross weight limit is in that document, at least for my aircraft.
It is wise to have weight and balance information in a POH or similar document for ready reference in the aircraft, but there is no regulatory requirement to have such a document. If you have such at document, it's contents are at your discretion. In the W&B info in my checklist I note the limit as "Van's recommended maximum gross weight is 2700 lbs."
As others have noted, if you decide to fly over the designer's recommended gross weight, you are eating in to the design safety margin.
I don't believe the FAA has any record of WB/GW on an EAB, and they don't need to be involved if you decide to change it.
The OP asked if GW can be increased legally and the answer is yes, is it prudent, that's up to the builder.
Keep in mind one of the first things on an NTSB report is if the AC exceeded GW, by any amount. If you did, you're immediately at fault.
The critical issue is CG. There are many examples of type certificated airplanes that had gross weight increases with no structural changes. One example is Piper Aztec which went from 4800# to 5200# with no structural changes.
Tip tanks on Piper Comanche and Twin Comanche allow a gross weight increase of 180# which is the weight of the tip tank fuel. IIRC the Max Conrad world record flight in the TC was at nearly two times the certificated weight of the airplane at takeoff. The tip tank increase only applies when there is fuel in the tip tanks.
Most metal airplanes are designed with a 1-1/2 safety factor. This means that a 6 G airplane was designed for a 9 G load.
Going above the designer's recommended gross weight cuts into the safety margin of the airplane.
Data and source or just anecdotal?The spelling is pseudo and is used incorrectly. A US type certificated aerobatic airplane with no maneuver restrictions will handle 7g every day for years. They do not start to bend at 6G. The Extras and similar airplanes with composite or partial composite structures are designed for plus/minus 10 G or more. The composite structure portions are designed for 20G, a safety factor of 100%.
If a pilot who has been flying a Pitts at 7G transitions to a monoplane he/she will likely be flying the monoplane between 8G and 10G within a few flights in the monoplane.
I guess we can disregard the design limits as you have shown them to be in error.The Pitts S2A was the first airplane type certificated in the aerobatic category for a long time. The S!S and S1T were later type certificated. The plus 6 minus 3 was simply a number required for certification. I personally saw a S1T at the nationals that showed 10 G. Curtis Pitts looked at that and had a big smile.
It is reasonable to believe that every S1S flown in airshows or competition was flown at 7 G positive and way over 3 negative.
Only one factory S1S ever has had a major structural failure. That airplane had a long history of abuse.
The original RV3 was presented as a 6G aerobatic airplane with certain maneuvers such as tailslides prohibited. Service experience proved the airplane was way less than a 6 G airplane. It took two major redesigns to fix the problem. On the other hand there has never been an inflight breakup of an RV6 and few if any with the RV4. Several with the RV7 and the one with the factoryRV8 which was probably a 10G or greater event.
The things working against the aerobatic RV's are the relatively light controls, the relatively low stall speed and the rate of acceleration following a loss of control. Vans "Aerobatic Epistle" explains how easy it is to put a 20 G load on an aerobatic RV. At the other end of the spectrum is the Sukhoi SU29 with that huge bubble canopy causing a lot of drag. From a hammerhead to Vne in the 29 takes 3500 ft vertical down with full throttle. In an RV6 I would guess you would go well beyond 300 m/h.
I do not advocate overloading any airplane. But as a practical matter in the aerobatic RV's going 100# over the published max gross is insignificant. The many long distance RV flyers have proven that. The racers have proven that speed is not the big deal that some make it. Personally in my non RV I am very comfortably flying over the design weight but not over Vne.
The numbers are not design limits but are the numbers presented to the FAA for certification.I guess we can disregard the design limits as you have shown them to be in error.
Great but those are NOT RVs.Multiple sources, published and personal experience. I flew my S1s at 6 1/2 to 7 for ten years. Sukhoi plus ten and minus seven for practice and a contest flight always seems to be 1 G greater. One of the first things I did in the Sukhoi was to high speed stall it pulling to vertical. Moderate speeds, probably half way between stall and Vne. It took 9 G to stall the airplane.
I built four Pitts S1S aircraft and rebuilt a couple others. The damage that I found on one rebuild was from taxiing into a solid object with the left lower wing.
Really. What engineering credentials do you possess to support this statement?The numbers are not design limits but are the numbers presented to the FAA for certification.
I did find a copy of the Analysis and design of flight vehicle Structures by E.F Bruhn online as an ebook. Just a fair warning it is pretty dense engineering.If you want to increase beyond the manufacturer recommended structural limits I recommend reading the following texts. When you can fully understand these you will have a good basis to do the calculations required to determine safe limits.
Airframe Structural Design & Airframe Stress Analysis and Sizing by Michael Niu $67-75 on amazon
Analysis and design of flight vehicle Structures by E.F Bruhn this one isn't in print anymore, but you can get used copies. They tend to be a bit pricy around $350
You are right it is not a requirement for EXPERIMENTAL aircraft.I wish it was not called a safety factor because it really is just a sudo aviation industry standard for two design points, when the structure could deform and when the structure could fail. metal will permanently deform before it fails. The 6 G limit load means the structure is designed to not deform before 6 Gs. The safety factor of 1.5 means the structure will not fail/crack/break before 9 Gs ultimate load but you could have permanently bent the structure any time above 6 Gs. For an RV-6A, which has a designed to max gross weight of 1650 lbs, if you increase max gross weight to 1800 lb you may get some structure to be permanently deformed at 5.5 Gs.
I will add my $0.02 which is "Why is 3.8G's a magic number for the normal category?" I realize it is the standard, and you need those for certification. But why 3.8? Why not 3.5 or 4 or something else? 3.8 seems fairly arbitrary.I am making an ASSUMPTION that any engineer worth his weight would attempt to design to FAR 23.2230 the same way I would.
I think the normal limit load for aircraft is 2.5 Gs. Multiply the safety factor which is 1.5, you get 3.75Gs. I am not sure 3.8 is round off but I think even the big boys use 3.75Gs to test the ultimate load, like the various popular wing break videos from the 777 or other large airplanes.I will add my $0.02 which is "Why is 3.8G's a magic number for the normal category?" I realize it is the standard, and you need those for certification. But why 3.8? Why not 3.5 or 4 or something else? 3.8 seems fairly arbitrary.
For light aircraft, normal is 3.8. Utility is 4.2, and Aerobatic is 6. All those numbers have a basis, but picking a specific number in any of those categories has a fair amount of "arbitrary" in it.I think the normal limit load for aircraft is 2.5 Gs. Multiply the safety factor which is 1.5, you get 3.75Gs. I am not sure 3.8 is round off but I think even the big boys use 3.75Gs to test the ultimate load, like the various popular wing break videos from the 777 or other large airplanes.
The design limit load factor of 2.5g applies to larger Part 25 Transport Category airplanes, not Part 23 GA airplanes. See Post #7.I think the normal limit load for aircraft is 2.5 Gs. Multiply the safety factor which is 1.5, you get 3.75Gs. I am not sure 3.8 is round off but I think even the big boys use 3.75Gs to test the ultimate load, like the various popular wing break videos from the 777 or other large airplanes.
Utility category load factor for light aircraft is 4.4 G’s (not that that matters in the context of this discussion since most people that fly over design gross weight don’t analyze that decision based on engineering and technical details).For light aircraft, normal is 3.8. Utility is 4.2, and Aerobatic is 6. All those numbers have a basis, but picking a specific number in any of those categories has a fair amount of "arbitrary" in it.
The 150% safety factor (ultimate load) is never considered by a designer to be used in the normal operation of an aircraft.I think the normal limit load for aircraft is 2.5 Gs. Multiply the safety factor which is 1.5, you get 3.75Gs. I am not sure 3.8 is round off but I think even the big boys use 3.75Gs to test the ultimate load, like the various popular wing break videos from the 777 or other large airplanes.
You know what they say about assumptions.You are right it is not a requirement for EXPERIMENTAL aircraft.
I am making an ASSUMPTION that any engineer worth his weight would attempt to design to FAR 23.2230 the same way I would.
You didn’t answer the question.
What's the difference between personal experiences and testing? It is data. Engineering calculations don't translate 100% accurately in the real world, that's why even engineers test after design. Sandbagging a wing, dropping an airframe to test the gear, or hydrotesting a pressure vessel, as examples.Great but those are NOT RVs.
Personal experiences do not substitute for data; published sources?
No, you do not understand the question, so I will ask again:I am sorry you do not understand the answer. I am not going to try and explain it to you.
So where is the data to support you statements concerning exceeding design limits?What's the difference between personal experiences and testing? It is data. Engineering calculations don't translate 100% accurately in the real world, that's why even engineers test after design. Sandbagging a wing, dropping an airframe to test the gear, or hydrotesting a pressure vessel, as examples.
I apologize. My comments were directed to someone who did. I replied to the wrong post, sorry.I didn't make any statement about design limits let alone exceeding them.
I never said that one should exceed the design limits.No, you do not understand the question, so I will ask again:
What credentials do you have to support you statement of using the engineering safety factor to exceed the design limits?
It seems short sighted to say that a higher aircraft weight would have zero influence.Regarding post 44, I don't believe either of those issue's were CAUSED by the higher gross weight. The issues with the landing gear portion of the engine mount are well known and are a design issue. The engine mount and gear leg damage are indicative of extremely hard landings. Additional possibility of improper heat treating of the gear legs.
I never said that one should exceed the design limits.