Increasing Gross Weight

[Danny7]

If someone was suggesting a max weight of 3000lbs I would understand all the back and forth on this. But, it seems to this builder that 1850 is a safe max weight, provided of course the CG is within limits. Am I missing something other than debating the accuracy of engineering limits. I say that with tongue in cheek because in my 40 years prior to retiring, I had several discussions with design engineers about why they added 40% to the restricted weight limits on certain steel structures. The answers were to add a safety margin. I shortened those conversations to the above statement to point out that in my opinion, engineering limits are not absolutes, especially with regard to the RV-6 or -6A. But, I'm just a builder who accepts the results of others who went before me with raised max gross weights.

at some point engineering limits are indeed absolutes. how close do you want to get to that limit, and what proof do you have of how far away you are from it?

for example, if someone wanted a max weight of 2100 pounds, i would have no problem with that if they did the proper weight test of the structures at the appropriate points along the structure. I've seen them done, and when they exceed the limit the result looks pretty absolute to me.

 

[L.Adamson]

Of course, once you've done all this, the performacne will suffer. Climb will be slower, and cruise slower as well (or it'll take a higher power setting for the same cruise). So you do reduce your margins by doing it. But you always have the *option* of flying lighter and quicker, or carrying more load slower and more carefully.

The good old "6" just must be a special airframe! And I suppose those extra 20 horses I carry over the 9's seem to make all the difference. My 6A is heavier than the 9's I fly with...............but it climbs faster, cruises faster, and can even match or exceed fuel efficiency if we all fly slower speeds together. This statement can be verified..

I'll argue as well as others, that the 6 has the beefiest wing structure of them all, with it's spar that meets in the middle. And if I remember right, even the A model gear legs are the same as the 7A's only a bit shorter. The 7 is rated at 1800 lbs. by Vans.

In the meantime, I'll happily carry full fuel when I begin flights over the treacherous mountains and deserts of the west...........instead of carrying less fuel to meet a gross weight of 1650, versus the 1850 that my 6A is set at.

And to Rob (Snowflake)------The Van's 6's are GREAT planes ! You'll like it!

L.Adamson --- RV6A

 

[N941WR]

...I'll argue as well as others, that the 6 has the beefiest wing structure of them all, with it's spar that meets in the middle. And if I remember right, even the A model gear legs are the same as the 7A's only a bit shorter. The 7 is rated at 1800 lbs. by Vans...

And I'll argue that the -6 is weaker than the -7 due to its lower Acro GW as set by the design engineers at Van's.

Be careful when setting a GW beyond what Van's recommends.

Rather than looking at the arbitrary GW set by the builder, you should look at the empty weight of the aircraft you are interested in.

 

[n5lp]

Alaska

No one has mentioned Alaska, where, due to some special air or the oil pipeline or something, maximum gross weight on many factory airplanes can be 15% higher than the standard maximum. 15% is a LOT! Same landing gear; same wing spar; different latitude and longitude. What does location have to do with structural engineering?

 

[L.Adamson]

And I'll argue that the -6 is weaker than the -7 due to its lower Acro GW as set by the design engineers at Van's.

Be careful when setting a GW beyond what Van's recommends.

Rather than looking at the arbitrary GW set by the builder, you should look at the empty weight of the aircraft you are interested in.

As I said before. I've been around these planes, too long, and know much about the six. Let's just say that it can handle more than in those old specs, and we'll let it go at that. In this case, we are careful.

P.S. --- Can't wait to see how well your rebuilt 9 will do. I don't care about top speed of course, but I bet the climb performance will be like night and day.

L.Adamson ---- RV6A / 1850GW

 

[Snowflake]

As I said before. I've been around these planes, too long, and know much about the six. Let's just say that it can handle more than in those old specs, and we'll let it go at that. In this case, we are careful.

I appreciate your confidence in the airframe, really, I do. I share your confidence after looking at many RV's under construction, that the -6 has a pretty darn beefy spar. But "you'll be fine" will never satisfy an insurance company, in the (hopefully) unlikely event of an accident. They'll ask what I was carrying. They'll ask whether it was within the limitations of the airframe. If i'm loaded at 1800 and crash, I can kiss any coverage I had goodbye. If I get ramp checked and someone looks at everything i'm carrying and decides to look closer, again, I could get violated for it. So i'm not keen on just flying and thinking "oh, it'll be fine." The Engineer in me knows that's neither prudent nor safe. I don't mind pushing limits, but I want to know what the limits are.

Your response indicates that you have more info that you're not sharing. I find that offensive, frankly, given the general willingness to share advice in this community. What you're saying is like going "nyah nyah, I have a higher gross weight and you don't, sucker!"

I've heard that Van apparently used to issue authorization letters for gross weights over 1600 for an RV-6, but I haven't been able to find a copy anywhere. I've heard that Vans Aircraft has said that aerobatic weights do not include fuel in the wings, but that is both hearsay and entirely counterintuitive, especially when 1375lb aerobatic plus full fuel is only a few pounds shy of Utility gross.

If you've got something that would help, please share!

 

[L.Adamson]

Insurance denied?

But "you'll be fine" will never satisfy an insurance company, in the (hopefully) unlikely event of an accident. They'll ask what I was carrying. They'll ask whether it was within the limitations of the airframe. If i'm loaded at 1800 and crash, I can kiss any coverage I had goodbye. If I get ramp checked and someone looks at everything i'm carrying and decides to look closer, again, I could get violated for it.

Since your GW is listed at 1600...... could be. In the meantime, I do go by the listed aerobatic weights. Since these two threads have been combined, go back a week or two, & look at some figures that were done for a Canada inspection. Part of the thread goes back a few years.

L.Adamson

 

[Snowflake]

I did go back through the entire thread, and all I could find was numbers listed as justification to an FAA inspector... Not something we have in Canada.

In Canada the rules changed recently, aircraft can no longer be declared at a higher gross weight than the kit manufacturer's recommendation at time of construction (for new aircraft) or import into Canada (for already flying aircraft). The aircraft must first be finished (or imported) at the design limit, and then an application submitted to increase the limit. The application presumably must be accompanied with some supporting paperwork, but I don't know what level of detail they want yet.

Again, if you have some useful knowledge that doesn't involve nudge-nudge-wink-wink "it'll be fine", please share.

My (unconfirmed) suspicion is that when Van designed the -6 he used an easy way of throwing in an extra safety factor: Only specify a gross weight at Utility category limits. This gives about a 15% safety factor on top of the Normal category limits. If the factory was willing in the past to give authorization letters to allow people to raise gross weights to 1800 (or 1850), it's possible that the letter also says "normal category gross" or some such. I'd love to know, but I haven't been able to confirm the existence of these mythical letters.

 

[Snowflake]

I think I found what you were thinking of... The other thread finishes with the steps necessary to get the GW increased on paper:

In a nutshell, they needed:
1) Letter requesting increase in MTOW. I included some info about g loading, weight and balance(important) and several other precautions that I was prepared to take at high weights.
2) Statement that there have been no changes to a/c config since original flight permit issued.
3) Confirmation w & B up to date, no changes.
4) Copy of log entry documenting climb test result. (I did 3 tests at increasing weights, 50# increments)
5) $35 fee.
6) New climb test report (form 24-0091)
7) Original Special c of A and operating conditions.

This addresses how to take care of the paperwork, which I still consider to be the easiest thing in the whole works. Sure, you can get TC to agree to a higher weight. The question is, how much less safe are you if you do it?

 

[Ironflight]

That looks like great research on the Canadian paperwork process Rob. I've been reading this thread as it developed, and I think there has been a great deal of "people talking past each other" for the simple fact that you have been talking Canadian regs, and others have been talking USA regs - plus you're talking about changing the GW on an already-registered airplane, and others are talking about setting the GW on a newly-built airframe. All different things, and all a different category from the engineering part of the deal!

In the USA, you don't need any letters from Van's, because they're not the manufacturer of the airframe....

Paul

 

[RV8R999]

Sorry, forgot about that question. it's common for airliners to have fuel dump valves to allow for this situation. It's possible for a homebuilt to have the same setup. But in an emergency situation, if you had to get back on the ground that urgently you would probably just risk the landing gear collapse and land anyway. If it's not that urgent, stay up, burn 50 lb of fuel off first, and then come back (assuming we're talking about the 1600 vs 1650 lb case).

Yeah no big deal, increase the gross weight based upon inflight spar loads (thanks for the Junior High algebra refresher), and accept the risk of a collapsed landing gear cause you've exceeded those limits..no big deal. Absurd. What about the effectiveness of the brakes at higher gross weight?

How about elevator angle per g during turning flight? Even the linearized equations (which are extremely simplified) include both the mass of the aircraft AND the static margin (cg) . It is NOT just about the spar loads . Your CG location is NOT the only factor in both the stability and CONTROLLABILITY of your airplanes. What about mass moment of inertia effect on pitch, roll and yaw rates? Your CG may be smack in the middle of the envelope but you still have to have the control power from the elevator, rudder and ailerons to move the mass around. How does this effect the dutch roll mode (since yaw damping and dihedral effect are most significant facotrs) or maneuvering stability? Regardless of the CG location it takes more force to move more mass about the CG..where does this force come from? All things being equal (DA, AS) at higher gross weight in level flight you are flying at a higher AOA, therefore your pitch moment coefficient is higher resulting in more elevator deflection at the trim point to maintain equilibrium which means you have less control margin before you hit the stops. How much less? Did any of the guys who claim to "know" their planes so well measure the margin? Or is it really good enough that you've gotten away without knowing all these years so it must be good? Hmmmm???

The point is that NOTHING in aircraft control, stability, and kinematics is simple and when somebody tries to convince you it is because they've done it 100 times (or 10000 times)...I'd watch out. Thats just me though.

 

[L.Adamson]

Yeah no big deal, increase the gross weight based upon inflight spar loads (thanks for the Junior High algebra refresher), and accept the risk of a collapsed landing gear cause you've exceeded those limits..no big deal. Absurd. What about the effectiveness of the brakes at higher gross weight?

How about elevator angle per g during turning flight? Even the linearized equations (which are extremely simplified) include both the mass of the aircraft AND the static margin (cg) . It is NOT just about the spar loads . Your CG location is NOT the only factor in both the stability and CONTROLLABILITY of your airplanes. What about mass moment of inertia effect on pitch, roll and yaw rates? Your CG may be smack in the middle of the envelope but you still have to have the control power from the elevator, rudder and ailerons to move the mass around. How does this effect the dutch roll mode (since yaw damping and dihedral effect are most significant facotrs) or maneuvering stability? Regardless of the CG location it takes more force to move more mass about the CG..where does this force come from? All things being equal (DA, AS) at higher gross weight in level flight you are flying at a higher AOA, therefore your pitch moment coefficient is higher resulting in more elevator deflection at the trim point to maintain equilibrium which means you have less control margin before you hit the stops. How much less? Did any of the guys who claim to "know" their planes so well measure the margin? Or is it really good enough that you've gotten away without knowing all these years so it must be good? Hmmmm???

The point is that NOTHING in aircraft control, stability, and kinematics is simple and when somebody tries to convince you it is because they've done it 100 times (or 10000 times)...I'd watch out. Thats just me though.

I see exactly what you're getting at, being a Navy test pilot and all,

But all of this has been previously hashed out in regards to the RV6/6A in the last 20 years. You are not pointing out anything new. It's been done far more than 10,000 times.

edit: No collapsed landing gear because of it, no loss of wings, and no unusual brake problems. Elevator control & all around control is phenomenal.

L.Adamson --- RV6A

 

[Snowflake]

I've been reading this thread as it developed, and I think there has been a great deal of "people talking past each other" for the simple fact that you have been talking Canadian regs, and others have been talking USA regs - plus you're talking about changing the GW on an already-registered airplane, and others are talking about setting the GW on a newly-built airframe. All different things, and all a different category from the engineering part of the deal!

They're all different in terms of what's needed to get to an end result, but they all have the same underlying question behind them: Is it *safe* to have a gross weight of 1800lb on an RV-6? Anyone can get the paperwork changed, that's not in question. Will you die if you do it, or maybe "how close will you get to dying", that's the question.

Not to sound overly dramatic.

Yeah no big deal, increase the gross weight based upon inflight spar loads (thanks for the Junior High algebra refresher), and accept the risk of a collapsed landing gear cause you've exceeded those limits..no big deal. Absurd. What about the effectiveness of the brakes at higher gross weight? etc. etc. etc.

You're right, there's a lot to consider. But a fair bit of this comes down to common sense too. Heavier plane will mean longer stopping distance, and longer takeoff roll too. Controllability margins will change too, and loads on tail surfaces and tail cone will all change. I'm an aeronautical engineer too, so give me some credit for thinking beyond the junior high math.

Most of the flight loads will scale proportionately to gross weight and g-loading, and i'm not proposing that there be any change to the combination of gross weight and G (at least not in my case). I'm suggesting a Normal category limit of 1800, a Utility of 1600, and Aerobatic of 1375. These numbers all work out (so far) in all of the analysis i've done as being essentially the same loading configuration, if you assume that the extra 200 lb goes entirely in the passenger cabin. No extra fuel, no extra heavy engine.

If people never tried pushing the envelope and modifying existing designs to improve them and expand on their capabilities, Van would never have built the RV-3 in the first place. And you might not be the envy of many pilots (myself included) as a test pilot for the Navy, you'd still be on the ground watching the birds wondering how they got up there.

 

[Mel]

Most of the flight loads will scale proportionately to gross weight and g-loading, and i'm not proposing that there be any change to the combination of gross weight and G (at least not in my case). I'm suggesting a Normal category limit of 1800, a Utility of 1600, and Aerobatic of 1375. These numbers all work out (so far) in all of the analysis I've done as being essentially the same loading configuration, if you assume that the extra 200 lb goes entirely in the passenger cabin. No extra fuel, no extra heavy engine.

These are essentially the same numbers that I've come up with.

 

[Ironflight]

I guess since Mel is on, maybe he can be dfinitive....My point in bringing up the difference in Regs is that I don't believe that Normal, Utility, and Aerobatic weights apply to Experimentals in any legal sense of the word in the US regs. If you are talking about specific G-loadings associated with those categories, then I am with you - but using the terms instead of the G-loads just confuses the issue between the engineering discussion and the paperwork discussion.

We are probably on the same page, just using different terms, and in engineering, words are how we make sure we are talking apples and apples....

As for the engineering/safety of it....I agree with the interesting aspect of Alaskan physics which pretty much arbitrarily allows 15% (I actually thought it was 10%, but memory is the first thing to go...) higher GW's for pretty much anything with wings. Interesting non-Newtonian place it must be...

Paul

 

[Mel]

You are correct that the different categories essentially do not exist for experimentals. I was using the terms as a guide as to how the aircraft should be operated.
Primarily, the load limits MUST be adhered to for aerobatic operations.

 

[Finley Atherton]

Both the RV9/9A and the RV6 have a max Utility category weight of 1600 lb (1750 max normal category for the 9/9A). My understanding is that the RV6 has an approved max aerobatic weight of 1375 lb. The RV9/9A is not approved for aerobatics at any weight. Anyone have any thoughts on why the 9/9A has no aerobatic max weight even though it has the same utility category weight as the aerobatic RV6?
Fin
9A
Note. I am just curious. I have no interest in, or desire to do aerobatics in my 9A

 

[jthocker]

No one has mentioned Alaska, where, due to some special air or the oil pipeline or something, maximum gross weight on many factory airplanes can be 15% higher than the standard maximum. 15% is a LOT! Same landing gear; same wing spar; different latitude and longitude. What does location have to do with structural engineering?

Interesting point Larry!
A long time ago when we were reviewing our CRAF(Civilian Reserve Air Fleet) contract with the government, I noticed some interesting things. During times of National Emergency when the fleet is activated (Airlines like Delta, American, Fed Ex, etc. basically fly charters for the DOD) those planes are allowed to fly at 10 % increased gross weight, mandatory maintenance times are increased by 10 %, and best of all, the flight crews max flight and Duty times could be increased by 10%!

Of course under normal ops. if a forlorn pilot shows up looking for a ride home and we were at gross wt. but had an empty cockpit seat, we'd be expected to leave him on the ramp!

Go figure!

 

[islandmonkey]

Both the RV9/9A and the RV6 have a max Utility category weight of 1600 lb (1750 max normal category for the 9/9A). My understanding is that the RV6 has an approved max aerobatic weight of 1375 lb. The RV9/9A is not approved for aerobatics at any weight. Anyone have any thoughts on why the 9/9A has no aerobatic max weight even though it has the same utility category weight as the aerobatic RV6?
Fin
9A
Note. I am just curious. I have no interest in, or desire to do aerobatics in my 9A

It is to do with the mission that the 9/9A was designed for. To quote Vans:

Blazing speed and "wring-it-out" aerobatics are not important for many pilots. Their day-to-day flying consists of local trips, relaxed cross-countries, and occasional long flights. The RV-9/9A was designed to do its best in this environment.

Hence the longer wing and different airfoil section.

 

[Kevin Horton]

No one has mentioned Alaska, where, due to some special air or the oil pipeline or something, maximum gross weight on many factory airplanes can be 15% higher than the standard maximum. 15% is a LOT! Same landing gear; same wing spar; different latitude and longitude. What does location have to do with structural engineering?

The laws of physics are the same in Alaska as they are south of the 49th parallel. But, the level of risk that people are prepared to accept is higher up there. Down south, a plane crash makes the news, but auto accidents are an accepted fact of life. Up in Alaska, light aircraft are just another means of transport, like a car down south, and aircraft accidents are much more acceptable.

 

[cguarino]

Maneuver speed

I might have missed it but did anyone talk about maneuver speed? Specfically, if I increase gross weight how do I calculate a new maneuver speed. I understand that some of the changes are offsetting but to what magnitude? Does anyone have a lift curve for the -4 wing that this info could be extrapolated? Thanks.

 

[Kevin Horton]

I might have missed it but did anyone talk about maneuver speed? Specfically, if I increase gross weight how do I calculate a new maneuver speed.

Manoeuvre speed is the speed at which the maximum lift the wing can create equals the design load that the wing structure can handle. The wing hasn't gotten any stronger just because you increased the gross weight, so leave manoeuvre speed as it was before.

 

[ScottSchmidt]

US Procedure

So what are the steps to take in the US if you have a plane flying already and you want to increase gross weight?
Does Phase 1 need to be repeated?

 

[Mel]

It's all there in your operating limitations.

To make a major change the aircraft must be placed back into phase I for a minimum of 5 hours for flight testing.
For changing gross weight, the aircraft must be flight tested to the new gross weight and balance limitations.

 

[tx_jayhawk]

Gross Weight and Insurance

Hi All,

Has anyone actually had an insurance claim denied due to exceeding gross weight?

Assuming one were to plan to fly their airplane slightly above Van's recommended gross weight, would it be better to have defined a higher weight on their speciifc airplane (and always fly it within that), or would it be better to stick to Van's numbers and hope that doesn't become part of the equation?

I'm assuming the prior, but I'm curious whether anyone has actually had any insurance issues as a result of actual loading.

Thanks,
Scott
7A

 

[Mel]

If you are going to fly above Van's recommended gross weight, you need to complete the change completely including testing to the new gross weight.
Without testing, how do know how the airplane will react to the new conditions?

 

[txshan130]

Experience with increasing RV-6 GW from 1600 to 1800

Hi Everyone,

Don't want this to migrate to a thread on the legalities of modifying the GW on the operating limitations...I am solely interested in people's experiences with successfully applying to the FSDO for an increase in gross weight over the Vans "recommended" 1600.

So is there anyone out there who has done this with positive results and actually gotten the FSDO to accept the change?

If so, what was your justification showing that it can be done? (besides the fact that many RV6s are initially given operating limitations with the 1800 lb GW.

Also, what was the process to get it done? How long?

Thanks so much for any & all replies!

- Brian

 

[flion]

No difficulty whatsoever. I don't think the subject ever came up; my DAR looked over my W&B and had me work some scenarios to put into my POH, but didn't blink an eye at the higher gross weight. I didn't go to 1800 but I did increase it.

 

[lockeed]

I'm interested in getting additionnal details on this.

Any of you know if it's possible in Canada also?

 

[Aden Rich]

Gross weight increase

I licensed my RV-6 at 1800lbs gross.
I put a .032 one piece top skin and did beef ups in the tail. However, I don't think you have to have these things.
The one thing I did do was get gear leg stiffeners and I fiberglass wrapped them (stiffeners on both sides of the gear leg). This really did help with dampening the loads when at higher weights.
I never had an issue and the plane barely noticed the increase as far as performance. (IO-360 and constant speed).
I just was careful about doing anything crazy as these weights. It was intended that I could have 2 200lb people, full fuel and 100lbs baggage. I would fly to somewhere and land at under 1600lbs.
I had to be careful about rear CG issues when all the fuel was burned off.

 

[Bob Axsom]

I just established my RV-6A gross wt at 1800 lb

Man what is going on with all this pussy footing around. You put down what you want and that is what it is. Van just supplies a product YOU are the EAB'r and there are no more limitations on you than if you scratch build your own one of a kind design. Van would like for you to limit your gross weight but the decision on what it is is up to YOU, not FSDO, DAR or Van. If you want to be conservative and prudent go with Van's suggested number but if you are only going to travel cross country with no aerobatics and you would like to take your spouse and a suitcase with full fuel then make another call - you are on your own either way.

Bob Axsom

 

[L.Adamson]

Man what is going on with all this pussy footing around. You put down what you want and that is what it is. Van just supplies a product YOU are the EAB'r and there are no more limitations on you than if you scratch build your own one of a kind design. Van would like for you to limit your gross weight but the decision on what it is is up to YOU, not FSDO, DAR or Van. If you want to be conservative and prudent go with Van's suggested number but if you are only going to travel cross country with no aerobatics and you would like to take your spouse and a suitcase with full fuel then make another call - you are on your own either way.

I'm not sure if its for an existing aircraft with a specified weight, or a new build.

 

[Bob Axsom]

Ah there's the rub

Sorry for the misinterpretation.

Bob Axsom

 

[Kevin Horton]

I'm interested in getting additionnal details on this.

Any of you know if it's possible in Canada also?

Yes, it is possible in Canada. Come up with a clear plan on how you will ensure you can safely operate at weights above Van's recommended gross weight then discuss it with your local Transport Canada office. They will tell you what they need from you before they issue a revised flight authority with the higher gross weight.

 

[az_gila]

Yes, it is possible in Canada. Come up with a clear plan on how you will ensure you can safely operate at weights above Van's recommended gross weight then discuss it with your local Transport Canada office. They will tell you what they need from you before they issue a revised flight authority with the higher gross weight.

Kevin, can you give us some idea of the actual weights that have been approved by Transport Canada?

 

[Snowflake]

There have been some rather spectacular gross weights listed in Canada for RV's. Well in excess of 2000lb for one particular RV-9A, as I recall. It was planned for a high-endurance flight and had extra fuel tanks everywhere... The mission expected straight/level/low-G flight, so a lower margin to failure was felt to be acceptable by the owner when operating at the higher weights.

Many people have registered RV-6's at 1800lb, and -6A's at 1850, 200lb over the recommended limits. There are rumours that Van used to issue a letter authorizing that increase that Transport accepted, but in 12 years I have not been able to find anyone who actually has one of these letters... Many people say "oh, a friend has one," but nobody has produced a copy. I'm starting to think they don't exist.

There is some logic in a Normal category gross of 1800/1850 on the -6/-6A, given the Utility category limit of 1600/1650, and Aerobatic limit of 13xx (forget the exact number) for both. But unless the extra weight is distributed evenly all over the aircraft, the logic falls apart pretty quickly.

 

[DeltaAlphaZulu]

It was planned for a high-endurance flight and had extra fuel tanks everywhere... The mission expected straight/level/low-G flight, so a lower margin to failure was felt to be acceptable by the owner when operating at the higher weights.

I'm at early RV-8 stage (empennage) but looking into increasing grosss weight for the same sort of reason, ie primarily long-range fuel. So that's my answer to part of the OP's post ie "What reasons have people done this?". But I see two main mission types: just me on long-distance flights (where straight/level/low-g would be the type of flight), and me plus pax on shorter or more "standard" flights eg $100 hamburger trips. So the current ideas on solving this is extra fuel tanks in the LE, ie almost full span tanks, but actual separate tanks that feed into standard / mains. That way, if I want or need to fly long hops myself, I fill the outboards. If I'm adding a pax and/or doing shorter trips I leave the outboards dry. But I suspect I will need increased gross to accomodate the extra fuel for the long ones.

 

[Andy Hill]

Darren...

Some quick points...

A typical RV-8 empty weight is 1100lbs. Add equipped pilot (200lb) & full fuel (250lb) and you still have 250lb "spare" e.g. for extra fuel i.e. you can double the fuel load and still remain within Vans GW if flying solo.

By the time you are into adding extra fuel tanks, I think you are in a different league to "just increasing GW" of the original design. You will need all the structural calculations of the effect of the tanks, and once you have done all these, then the GW should be easy.

 

[Wallbangar]

Overgrossed c.g.

C.G. is not what I worry about so much. There is a point in the summer time when a 1900 pound RV 7 will fly level only (no climb) at 5000 feet density altitude. BUT DON'T TRY THAT NEAR DENVER IN THE SUMMER TIME !!!!!!!!!!!

 

[ChiefPilot]

C.G. is not what I worry about so much. There is a point in the summer time when a 1900 pound RV 7 will fly level only (no climb) at 5000 feet density altitude. BUT DON'T TRY THAT NEAR DENVER IN THE SUMMER TIME !!!!!!!!!!!

Seriously? With what engine & prop?

 

[mikerkba]

High DA performance

C.G. is not what I worry about so much. There is a point in the summer time when a 1900 pound RV 7 will fly level only (no climb) at 5000 feet density altitude. BUT DON'T TRY THAT NEAR DENVER IN THE SUMMER TIME !!!!!!!!!!!

I find the above limitation on performance not accurate on my plane. I just lost a longer post, but here is the summary:

September, 2011
Departure runway elevation 6250 feet at KELY
Departure DA 9000 feet
RV7A, 180 HP, CS prop.
Total weight with two SOB, 50 gal fuel, oxygen, and bagage = 1861 lbs.
Initial climb of 550 to 600 fpm. Continued climb up to 11,500 enroute to Billings, MT
After 2.5 hours (and 120 lbs of fuel were burned off) continued climb to 16,000 to try to top some clouds. Plane quit climbing at 16,000.

When solo, I've never had trouble getting to 17,500 feet regardless of temperatures, but the climb does slow to 400-500 fpm near the top, of course.

 

[Mel]

I also find that prediction difficult to understand.

I have flown my RV-6, granted not at 1900lbs., out of Leadville, CO (9926') (DA=13,400') in the summer with 150 hp and fixed pitch wood prop and it was still climbing very well at 14,500' with no problems whatsoever.

 

[Rosie]

I also find that prediction difficult to understand.

I have flown my RV-6, granted not at 1900lbs., out of Leadville, CO (9926') in the summer with 150 hp and fixed pitch wood prop and it was still climbing very well at 14,500' with no problems whatsoever.

I'm with Mel.... I once flew out of Leadville with full fuel at gross weight (~1800 lbs), density altitude of 12.5K and climbed out at 800 ft/min (180hp/fixed pitch) to 15.5K westbound, also with no problems whatsoever Rosie

 

[Ron Lee]

My first trip to Leadville was during my mountain flying course. RV-6A, 180 HP, Fixed pitch prop. Density altitude on take-off was at least 12,000' and there was about a 15 knot crosswind. Got airborne just fine. Obviously not the climb performance as near sea level but no doubt far better than a Cessna 172.