I weigh too much.

[Witch]

Ok, so we all know that the max TO weight of a Robbie is 1370 lbs. Here's a stupid topic that a couple of us were discussing; how much weight can you put into a Robbie before it won't lift off? Figure a standard day with no wind, and no running takeoff either.

 

This came about because I posed the question that in a 60* bank, the machine weighs over 2700 lbs, and so the rotor can at least support that weight. If so, then if the bird can handle that, can it handle flying over max weight by say 50 lbs?

 

Mind you, this is an exercise, so please keep the safety comments to a minimum. Thanx.

 

Later

[helidave]

If so, then if the bird can handle that, can it handle flying over max weight by say 50 lbs?

 

Mind you, this is an exercise, so please keep the safety comments to a minimum. Thanx.

 

Later

 

 

 

The machine can handle 1370 lbs max Any more than that and you're a test pilot. The question isn't really if it will get off the ground at 50lbs over MTOW, it's how long will it stay off the ground before parts start flying off.

 

Also, that 2G's at 60* bank is just a generic example. You wouldn't be able to maintain altitude in an R22 past about a 45* bank angle.

Edited October 27, 2007 by helidave

[Witch]

The machine can handle 1370 lbs max Any more than that and you're a test pilot. The question isn't really if it will get off the ground at 50lbs over MTOW, it's how long will it stay off the ground before parts start flying off.

 

Also, that 2G's at 60* bank is just a generic example. You wouldn't be able to maintain altitude in an R22 past about a 45* bank angle.

 

Sorry Dave, that weren't my question.

 

How much weight can you put into a Robbie before it won't lift off? Figure a standard day with no wind, and no running takeoff either.

 

Just an exercise to determine a value, that's all.

 

BTW, I don't think that being overweight will cause the machine to fall apart.

 

Later

[apiaguy]

Well, I'm no robbie expert but I'll give you a Schweizer comparable.... the gross weight on the 269A is 1670 lbs.

If standard day like you say then I can theoretically pull about 27 inches at our airport elevation.... at max gross weight it usually takes about 23-24 inches to hover @ 2-3 feet. I estimate it takes about 1 inch of manifold to lift 100 lbs near gross weight... so I believe it would lift an extra 300-400 lbs into a hover.... the problem would be keeping the cg in an acceptable range... but if it was on a hook it could do it.

 

So if your robbie lifts off at say 21 inches manifold and limit is like 24 or something (remember I don't fly robinsons) then I would suspect it could lift a couple hundred extra pounds into a hover.

Try to figure how much manifold difference there is when there are two aboard vs. solo. That difference in manifold divided by the weight of the other person should give you a rough idea of how much extra weight the thing would lift.

 

I know this answer is kinda hodge podge but I'm giving it a try... yes the thing will lift 50 over gross easy!! I'd say a couple hundred over gross if you're near sea level.

Edited October 27, 2007 by apiaguy

[PA Pilot]

Sorry Dave, that weren't my question.

 

How much weight can you put into a Robbie before it won't lift off? Figure a standard day with no wind, and no running takeoff either.

 

Just an exercise to determine a value, that's all.

 

BTW, I don't think that being overweight will cause the machine to fall apart.

 

Later

The problem is that because of the derated engine, you can lift off significantly over gross. That in turn overstresses the transmission and blades and possibly spindles and other components. Do it enough times and something will fail. Read the safety notices on Robinson's web site for more.

[500pilot]

Here's a link to what happens when you are over max gross weight.

 

http://www.ntsb.gov/NTSB/brief2.asp?ev_id=...A056&akey=1

Edited October 27, 2007 by 500pilot

[Goldy]

Ok, so we all know that the max TO weight of a Robbie is 1370 lbs. Here's a stupid topic that a couple of us were discussing; how much weight can you put into a Robbie before it won't lift off? Figure a standard day with no wind, and no running takeoff either.

 

This came about because I posed the question that in a 60* bank, the machine weighs over 2700 lbs, and so the rotor can at least support that weight. If so, then if the bird can handle that, can it handle flying over max weight by say 50 lbs?

 

Mind you, this is an exercise, so please keep the safety comments to a minimum. Thanx.

 

Later

 

OK, I'm keeping the safety comments to minimum. However you also said "BTW, I don't think that being overweight will cause the machine to fall apart"...actually the answer to that question is ..yes, it will, you just dont know when.

 

The R22 is a light machine, it is built to only handle certain stresses when operated within the POH limits. When you overload it...it will fail, but just maybe not when youre flying it, maybe when the next poor guy flies it.

 

Now back to the original question. Close to sea level, with the power of a BetaII, you could probably hover in ground effect with an extra 250 pounds or so. Probably get airborne at 1500. I often fly my R22 at 1370 take off weights, just cause I'm a big guy so it doesnt take much to get there. Rarely can I take on much more than 2/3 tanks of fuel, and on hot days I leave them at half tanks. I have several W&B pre calculated so its easy to determine just how much fuel I can carry.

 

Australia is famous for their fatal R22 accidents, and famous for flying when overloaded. Read some of those reports, their investigations are even better than NTSB's...( apologies to any NTSB officials).

 

Remember that engine can crank out 200 HP, yet the transmission can only handle 130hp..it will probably be the first to fail, with the blades and spindles next. The engine doesnt care ...great little motor, lots of power.

 

Kids, dont try this at home. Fly within the POH. enough said.

Goldy

[Gomer Pylot]

Any helicopter will hover above gross weight under at least some conditions. That's what performance charts are for - to tell you at what weight the helicopter will hover in and out of ground effect under the given conditions. Hovering above max gross weight may or may not require exceeding any other limitations, and often won't. The max certificated gross weight is a limit for the landing gear in addition to any other limits, so whether it will hover, and whether any other limits are exceeded doesn't make a lot of difference. The limits are always conservative, so exceeding the max weight by a few pounds shouldn't cause a catastrophic failure. I know with absolute certainty that I've taken off over gross more than once, or at least tried to, because the critters just lied about their weight, and/or their baggage/cargo weights. Sometimes it wasn't immediately obvious, and sometimes the helicopter just wouldn't hover at all. It depends on the temperature, the density altitude, the wind, and the humidity, among other things. You don't want to ever intentionally exceed any limit, but sometimes it happens. That's another reason to be slow and smooth with your liftoff, hover, and takeoff. If you're careful, you can see what performance you're getting before you're committed to anything.

[Witch]

Thanks Gomer, your posts are often great sources for insight and information.

 

PA and Goldy; I guess I should have made the assumption that the drive train could handle the stresses. Also, assume the weight stays within the GC envelope.

 

500; The thing that gets me about that report is that the ship had been flying for quiet a while-"The GPS began recording at 0937:34, and ended at 1102:52". The weight too was over gross-"At takeoff, the estimated gross weight of the helicopter was 1,485 pounds". Also, since the carb was dry, it's logical to assume that the reason for the crash was fuel starvation, not the weight. I'm not going to debate if that was the cause or not, I'm just looking for an assumption to a theoretical question.

 

Apia has an answer that seems reasonable. The Robbie might put out 190 hp which translates to about 1540 lbs that might get it barely off the ground. That's about 170 lbs over gross. I realize that there are other factors involved.

 

That said, although 20-30 lbs over might not be that big of a problem, I still want to avoid that as much as possible.

 

Later

[TheLorax]

Here's a stupid topic

 

definitely.

 

safety first!

[southernweyr]

"The carburetor was removed and examined. The carburetor halves were then separated, and a small amount of light blue fuel was found in the bowl."

 

"The main fuel tank was intact, but empty, and the cap was secure. The auxiliary fuel tank was removed and examined. The cap was secure, but the interior side of the tank was ruptured in several locations. Approximately 16 ounces of fuel was found in the bottom of the tank.

 

When the helicopter was righted back onto its skids, fuel drained from several underside locations."

 

This seems to say that fuel starvation was not a factor.

[jehh]

Ok, so we all know that the max TO weight of a Robbie is 1370 lbs. Here's a stupid topic that a couple of us were discussing; how much weight can you put into a Robbie before it won't lift off? Figure a standard day with no wind, and no running takeoff either.

 

At sea level? I'd agree with the other answers and say about 1,500 lbs...

 

It won't last until 2,200 hours if you keep doing that however.

 

This came about because I posed the question that in a 60* bank, the machine weighs over 2700 lbs, and so the rotor can at least support that weight.

 

The rotor can handle it for a few seconds, it cannot handle it for a long time.

 

If you take off at 1,500lbs, then make a steep bank, you're going to end up well over the design limit, and then it might not support it. Also, your autorotation performance may or may not get you on the ground.

 

Having flown a R-22 at sea level, then again at 8,000ft, I can tell you from personal experience that just looking at weight is not enough. This is why there are performance charts, because it cannot handle the same weight under different conditions.

 

Also, just because it will take off doesn't mean you should... The engine can produce a lot more power than the tranny and spindles can handle, fly around at 27" of power for awhile and the helicopter will bite you sooner or later.

 

Anything outside the limits makes you a test pilot, and I doubt you're paid enough to be one of those.

[southernweyr]

Anything outside the limits makes you a test pilot, and I doubt you're paid enough to be one of those.

 

 

That's for sure.

[delorean]

Here's a link to what happens when you are over max gross weight.

 

http://www.ntsb.gov/NTSB/brief2.asp?ev_id=...A056&akey=1

 

Do you (or anyone) know anything more about this accident? Mainly the pilot?

 

My memory is clouded on how this went, but I believe he was going around to flight schools renting helicopters for "personal use" and but was using them for commercial and 135 use. There was more to it though. Very strange circumstances....it's coming back, with some help.

[delorean]

There's a Robinson SB out about looking for compression cracks on top of the blades perpedicular to the leading/trailing edge about 2-3 inches out from the root. A direct result of extreme overloading of max gross weight.

 

Never had this problem with the Standard, HP, Alpha, or Beta in 16 years. It happened when they went to the Beta II with the bigger engine. Suddenly all the pilots would were overloading the a/c by 100+ lbs on a regular basis could now overload it 200+ lbs.

 

They gave the helicopter enough power to break itself.

[Gomer Pylot]

The ratio of engine power to transmission capacity is a design decision. You can match the engine to the transmission at sea level, and at a few thousand feet you will hit engine limits very quickly, and hover performance will be poor. You can make the engine(s) much more powerful than the transmission can handle, and the aircraft will perform well at high altitudes, but the engine can destroy the transmission at sea level if torque limits aren't observed. The engine can be derated, but I've never seen the advantage of doing this. My preference, and that of most pilots, is to have all the engine power available I can get, and it's my responsibility to stay within all limits. With a properly designed system, you'll never reach engine limits at or near sea level, or indeed even come close. That's one of the advantages of flying in the Gulf of Mexico - there is almost always plenty of engine power available, unless you're flying a very old model. But in seriously high mountains, you may reach engine limits before torque limits. It's a balance the manufacturer has to make, because the more powerful the engine, the more expensive it is, and usually the more fuel it burns. Everything is a compromise, and TANSTAAFL.

[Chi-town]

I know I'll sound like a jerk for saying this, but I reread Witch's original post to make sure I wasn't overreacting, then I reread the replies. Save for a few other souls who couldn't help but raise the safety flag, most entertained the mental exercise in stupidity.

 

There should be NO reason to ever overload the Robbie. You're not flying in to a hot LZ to pick up loads of wounded GIs, you're not rescuing flood victims from New Orleans, etc. I just feel really nervous when a flight student is already entertaining "hypothetical" violations of the POH and already dismisses common warnings and cautions as myth (parts and components will stress, wear faster, and eventually fail catastrophically when flying overloaded aircraft). When a student who should still have reverential respect for every word in the POH is already questioning these things, I fear what kind of boundaries we'll be crossing when you're an instructor.

 

Witch, I've been reading your posts for a while and I know you have your head screwed on straight. I just cringe when people start "what iffing" when it comes to Robbies and their limits.

 

I know old Frank Robinson has "cushions" built in to his limitations, but that is the realm of the factory test pilots. As a future instructor, you need to be a downright fascist when it comes to conservative, by-the-book flying as an example to the students.

 

Anyways, I'm sorry if I sound like a jerk, and I know you probably are super-safe. I just couldn't let this subject pass for the sake of other young pilots out there who might want to become junior test pilots.

Edited October 28, 2007 by Chi-town

[Chi-town]

!

Edited October 28, 2007 by Chi-town

[TheLorax]

although i think it is the students job to question and contort (while not actually going out and doing the stupid things), i agree with Chi-Town.

 

For example... I am the type of person who will push the proverbial 'button' if there is a button available to push. I will push an unmarked button, just for the sake of pushing the button. I need to test limits and become accustomed to whatever it is I need to become accustomed with.

 

A way to do this in helicopter training without actually pushing any "buttons" or disengaging the "clutch" in mid flight, is to ask retarded what-ifs to your instructor or to fellow VR posters.

 

I will never fly an r22 if it's above 1370.

[Goldy]

I will never fly an r22 if it's above 1370.

 

I am in total agreement, I never fly over 1370..in my BII. Remember the earlier versions are 1300 limits.

[Witch]

Chi,

 

You don't need to raise the safety flag.

 

There're two FI's at the school-well, 2⅝-, and I'm wanting to get opinions from others. These guys aren't gonna let me do some of the things they've told me, such as a roll-as long as it has rigid blades. Believe me, I'm not going to fly overweight...much...and I'm not going to land on a train, and I'm not going to leave the helo running while I get out to open a gate (for the cattle) like I've heard some Kiwi's do.

 

Gomer and Apia have given their thoughts about the "What if" as just that, what if. It's to think about scenerios or situations that get one to thinking a little different about flying. We know engineers over build things-or hope so, and so taking that into consideration, what could one do to get the most out of that machine. It's a therotical game of sorts.

 

I hope that was clear. Sometimes I don't do so well explaining my thoughts.

 

Anyhow, don't take me too seriously, unless you're in the copter with me and we're shooting Hellfires at one of those ships from Independance Day. Area 51 does exist, dammit!

 

Later

[RotorWeed]

I am in total agreement, I never fly over 1370..in my BII. Remember the earlier versions are 1300 limits.

 

We were taught at “Robbie School” the only reason for the increase from 1300 to 1370 on the beta 2 is the Aux fuel cell. You don't really gain anything other then the extra gas.

 

Aux Fuel tank weights 10 lbs

Fuel in the tank is 60lbs

Hence the extra 70lb increase in gross weight.

[Sparker]

We were taught at “Robbie School” the only reason for the increase from 1300 to 1370 on the beta 2 is the Aux fuel cell. You don't really gain anything other then the extra gas.

 

Aux Fuel tank weights 10 lbs

Fuel in the tank is 60lbs

Hence the extra 70lb increase in gross weight.

 

hmmmmmm.... should I feel safe?

[delorean]

hmmmmmm.... should I feel safe?

 

Yes, because it didn't have anything to do with max gross weight.....it was because of C.G. On anything without a aux tank, there's no way you could have put anymore weight in that helicopter without falling out of the forward part of the C.G. envelope.

 

When they went to the Beta model, the battery was moved very close to the basic operating weight C.G. line and the aux tank (and any fuel in it) went behind that line. So by adding weight, they were able to allow more cabin weight. Strange how it works out, huh?

[RotorWeed]

Yes, because it didn't have anything to do with max gross weight.....it was because of C.G. On anything without a aux tank, there's no way you could have put anymore weight in that helicopter without falling out of the forward part of the C.G. envelope.

 

When they went to the Beta model, the battery was moved very close to the basic operating weight C.G. line and the aux tank (and any fuel in it) went behind that line. So by adding weight, they were able to allow more cabin weight. Strange how it works out, huh?

 

This is true; however it’s not a significant increase in capacity in my opinion.

They moved the battery from the instrument panel to behind the left seat; added

Aux tank, and bumped up the gross weight 70lbs.

It’s not like we get a huge increase in weight carrying capacity on the beta 2.

I feel sorry for the IFR trainer folks; they must have a really critical CG issue with two large pilots, and fuel.

I guess they want us to trade in our 22’s on a new 44.