Flying Overweight!
Thread Starter
Joined: Mar 2006
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From: scotland
Flying Overweight!
Before I ask this question can I say that I don't ever,ever fly my heli overweight and for this reason I an 44'ing in a Robbie now as opposed to 22'ing it, However, I wondered if anyone can answer a query brought up by a pal who I was flying with and laughed when I took 4 gallons out of my 22 before we took off. It obviously applies to all helicopters.
If you fly at the max allowable weight, take off and do a 60 degree series of banks, perhaps to inspect something below, the helicopter is effectively twice its weight! Even at a 30 degree bank the load on the blades etc is such that the helicopter is much heavier. So when they spec the max allowable weight are they taking that into account and if so does that mean there is a huge safety margin in normal straight and level flight?
No replies please about insurance being invalid etc etc, as I said at the start I don't ever do it but it was a valid question and one I couldn't answer!
If you fly at the max allowable weight, take off and do a 60 degree series of banks, perhaps to inspect something below, the helicopter is effectively twice its weight! Even at a 30 degree bank the load on the blades etc is such that the helicopter is much heavier. So when they spec the max allowable weight are they taking that into account and if so does that mean there is a huge safety margin in normal straight and level flight?
No replies please about insurance being invalid etc etc, as I said at the start I don't ever do it but it was a valid question and one I couldn't answer!
Joined: Dec 2003
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From: The South
bvgs,
I think you will find that most MTOWs are a structual limitation due to the weight that the skids can take. Some aircraft have a higher all up mass with an underslung load.
I am sure the respected authorities that post on this forum will enlighten us all.
FNW
I think you will find that most MTOWs are a structual limitation due to the weight that the skids can take. Some aircraft have a higher all up mass with an underslung load.
I am sure the respected authorities that post on this forum will enlighten us all.
FNW
Joined: Apr 2003
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From: USA
Note: Discussion of exceeding limits is made for education only, breaking the limits is illegal, unethical, and unwise
bvgs uses impeccable logic, and is quite correct:
The structurally the MGW is a fuzzy number, from a limits standpoint, because even a small 0.1 g bit of air turbulence gives you a 10% increase in all-up weight, if but for a few seconds. Clearly, the aircraft will not fall apart if you overload by a few percent. Similarly, the skids, engine mounts and other fixed bits of structure see loads on landing that are quite a bit higher due to the accelerations that they experience, so that a few percent is not a big factor. Nonetheless, each bit of increased loading due to overweight makes the structure experience a bit faster life degredation, so that the time limited components lose life faster, and will produce cracks earlier, perjaps within their safe life. For that reason, overload is a bad idea, but might look ok in the short term.
A worse situation is seen in the flight performance arena. Each pound of extra weight takes a great deal of performance off the table. Look to the hover charts and deduce the loss in hover IGE altitude for each 100 lbs of MGW, and realize that very quickly, a helicopter turns into a lead sled with even a few % overload. Hover altitude, tail rotor authority, climb rate and single engine performance all suffer rapidly with even modest increases in MGW above limits.
Joined: Jul 2005
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From: North
If you are close to or exceed the Max Weight then you might notice that the 'coning angle' also increases. This will reduce performance in all modes of flight since the RAF and IF values will change. You might detect when you have got your figures wrong by the fact that when you enter a 60/60 there appears to be a marked increase in vertical bounce which will increase as you roll on the manouvre. Any irregularity in tracking and balancing will cause the onset of this 'vertical bounce' to ocurr at an earlier point - ie at the begining of the manouvre before fully established and or below the max aum. Another good indicator of a cock up in your calcs - next time you fly try flying an approach to fixed and specific data and note the weight. Now increase the weight and try the same approach to the same data. Assuming you have a steady and similar wind etc then you might note the required power value. I have found in the past that the power required during approach is a good warning of what is to follow.
Joined: Jan 2005
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From: yorkshire uk
Come on , there is overweight and there is OVERWEIGHT !!!! No way would i take 4 gallons out....unless i was in a Robbo or in a very tight LZ requiring a high vertical take off. I flew quite regularly grossly overweight , for the conditions....Egypt ...hot etc, due to people forgetting to turn the pump off when putting the chemicals in.!! The aircraft should fly normally and if you have good long area to transition from /to forward flight there is no power issue. Obviously in the event of engine failure you may contact terra firma slightly harder and the cross tubes /skids may fail. As for wear etc what about all the trips you do solo with low fuel ? surely that takes the pieces out of the jar much slower ?
This is NOT advocating flying over MAUW but in a working environment it does happen, also as stated earlier ,the figure given is skid related and the aircraft is probably quite capable of lifting much more and flying safely.
This is NOT advocating flying over MAUW but in a working environment it does happen, also as stated earlier ,the figure given is skid related and the aircraft is probably quite capable of lifting much more and flying safely.
Guest
Posts: n/a
don't forget the R22 has a low seat weight limit of 240lb - as I found out to my cost once....
I was 10 lbs over at the time and I was told I couldn't fly at the weigh in ! Operators in the States take this very seriously - not so much in the UK though, from experience.
I was 10 lbs over at the time and I was told I couldn't fly at the weigh in ! Operators in the States take this very seriously - not so much in the UK though, from experience.
Thread Starter
Joined: Mar 2006
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From: scotland
The machine in question re the 4 gallons was an R22 and I was about to fly for over an hour to my destination, half an hour into the flight I would have been back within limits but I still took the 4 gallons out am I being paranoid. I recall in my early days, when being taught, that myself and instructor should only have allowed 20 gallons and there were times we flew on full tanks (30GALLONS). When I had enough knowledge to question it, he said he was lighter than he looked but it never happened again after that.
Joined: Feb 2006
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From: In my Hammock or at the Pub!
Please Explain
Originally Posted by nigelh
I flew quite regularly grossly overweight ......, This is NOT advocating flying over MAUW but in a working environment it does happen...... and the aircraft is probably quite capable of lifting much more and flying safely.
Limits are limits-Exceed them at your own and your pax cost, and no I'm not new to the industry and YES I have been operating commercially long enough to have experienced all types of clowns asking to do stupid things in machines. The answer is always no to clowns!
Max
Joined: Aug 2003
Posts: 426
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From: Australia
Get a grip!
I run a Robbie safety programme.
Why all the failures in years gone by - and recently R44 overweight out of CG and incidents.
Can't add up?
You should not fly a modern machine overweight. It is designed to fly to the service life, provided you keep in limits. Older machines had sort of a "fudge factor".
So why do it?
Why all the failures in years gone by - and recently R44 overweight out of CG and incidents.
Can't add up?
You should not fly a modern machine overweight. It is designed to fly to the service life, provided you keep in limits. Older machines had sort of a "fudge factor".
So why do it?
Joined: Jul 2001
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From: the cockpit
Back to the jelly bean jar again....
The aircraft will tolerate the over all up weight ops to a point, but as Nick points out, NONE of the service life, inspection intervals, or replenish requirements are calculated on you flying over weight. When you do it, you are using the jelly beans faster than designed. But is it you who ends up with the empty jar?
The amount of fatigue failures that can be directly attributed to overstress (over weight, over temp, over speed, over TQ, etc) is phenomenal. But how often is it that the pilot who overstresses is the pilot that ends up suffering the failure and its fatal consequences?
I think that pilots who use the jelly beans faster than designed, and dont tell anyone so fatigue life and inspections can be adjusted, are a pox on the earth. Especially if someone subsequently gets killed or injured. Imagine that when you are next just fudging it a bit.
No disrespect meant Nigel as I am sure there were other circumstances at play, and I am well aware of how times and education have since changed both peoples' tolerance and perception of the type of operation you describe. And I know you will agree that those days are over.
The machine will take it, but we now know that flying over all up weight is totally disregarding the life and welfare of your fellow pilots and their families. No matter how you justify it to yourself .
The aircraft will tolerate the over all up weight ops to a point, but as Nick points out, NONE of the service life, inspection intervals, or replenish requirements are calculated on you flying over weight. When you do it, you are using the jelly beans faster than designed. But is it you who ends up with the empty jar?
The amount of fatigue failures that can be directly attributed to overstress (over weight, over temp, over speed, over TQ, etc) is phenomenal. But how often is it that the pilot who overstresses is the pilot that ends up suffering the failure and its fatal consequences?
I think that pilots who use the jelly beans faster than designed, and dont tell anyone so fatigue life and inspections can be adjusted, are a pox on the earth. Especially if someone subsequently gets killed or injured. Imagine that when you are next just fudging it a bit.
No disrespect meant Nigel as I am sure there were other circumstances at play, and I am well aware of how times and education have since changed both peoples' tolerance and perception of the type of operation you describe. And I know you will agree that those days are over.
The machine will take it, but we now know that flying over all up weight is totally disregarding the life and welfare of your fellow pilots and their families. No matter how you justify it to yourself .
Joined: Apr 2003
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From: USA
Sometimes you have to break the rules. I flew about 1,000 hours in AH-1G Cobras that were at 10,700 lbs, vice their max gross weight of 9,500. Rotorhead parts were constantly wearing out, and we were always running out of tail rotor authority. When I asked my CO why we were breaking the rules, he said, "What do you want to leave home - the bullets or the gas?"
Joined: Dec 1999
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From: UK
There are only two occasions whan this sort of thing is ever acceptable, and then only in extremis.
There is a paragraph in the ANO that says something to the effect of "above rules do not apply in the case of saving life", sometimes referred to as the "life and limb" clause.
And as Nick said above, when there's a war on...
Neither of which will ever apply to 98% of us.
Remember, there's usually a paper trail, and if you bend your cab one of the first things the investigators will look at is weight, and project it back to take off. It's pretty simple. Bust weight and you're risking fines, perhaps klink, unlimited personal liability if others are hurt or even just a bit frightened (traumatized!!!) and certainly the wrath of everyone as the insurance company will just laugh. And serve you right.
There is a paragraph in the ANO that says something to the effect of "above rules do not apply in the case of saving life", sometimes referred to as the "life and limb" clause.
And as Nick said above, when there's a war on...
Neither of which will ever apply to 98% of us.
Remember, there's usually a paper trail, and if you bend your cab one of the first things the investigators will look at is weight, and project it back to take off. It's pretty simple. Bust weight and you're risking fines, perhaps klink, unlimited personal liability if others are hurt or even just a bit frightened (traumatized!!!) and certainly the wrath of everyone as the insurance company will just laugh. And serve you right.
Thread Starter
Joined: Mar 2006
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From: scotland
Do we then conclude that a heli that has been used for say Ariel work when it will spend alot of its time circling above specific targets to get the right shot, will be more likely to have expired parts than one thats used to ferry guys to and from the golf? Lets face it you can't have it both ways. Either they spec it for doing a load of 30-60 degree banks at full weight, work out the load and recalculate what the total permisable weight should be or they assume an average of 30-60 degree banks and work it out that way?
Totally agree not to fly overweight(first sentence in this thread) Just wondered how its calculated when there are such variables??
My original question was not whether you should or shouldn't fly overweight
Totally agree not to fly overweight(first sentence in this thread) Just wondered how its calculated when there are such variables??
My original question was not whether you should or shouldn't fly overweight
Joined: Apr 2003
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From: USA
The lives of components is based on guesses as to the use (called usage spectrums) that are used to factor the loads and number of cycles at the loads. The FAA/JAA must approve the spectrum that any given type aircraft has, but it is always a melange of the many missions that one can perform.
Even those aircraft that are continuously turning don't see all that much extra load, because they are not continuously turning.
Thos that do many power cycles are the ones to watch - 5 minute takeoff followed by approach and then another takeoff.
In any case, the spectrum is the thing, and it is an educated guess. This has been discussed in 10 or so threads in the past, and yes, HUMS could be used to help know how many cycles were experienced, but it is not allowed to be used for that, yet.
Even those aircraft that are continuously turning don't see all that much extra load, because they are not continuously turning.
Thos that do many power cycles are the ones to watch - 5 minute takeoff followed by approach and then another takeoff.
In any case, the spectrum is the thing, and it is an educated guess. This has been discussed in 10 or so threads in the past, and yes, HUMS could be used to help know how many cycles were experienced, but it is not allowed to be used for that, yet.
Joined: May 2005
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From: Missouri, USA
I was taking my checkride in an R22 a couple of months ago and the examiner said he was 235 lbs. The max psgr weight is 240 and when I saw him for the first time the morning of the checkride I wasn't sure what to say. Helluva nice guy, but I'd have guessed somewhere between 250-270 lbs. We strapped in and the poor machine struggled to lift its skids, max manifold pressure, and I didn't waste any time getting forward movement. We went through a few maneuvers and when it was time for the simulated engine failure we dropped like a rock. I pulled back on the cyclic, and back, and back. "whoa, fella!"
PPRuNe Enigma
Joined: Feb 2001
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From: Scotland
Indeed - at least while doing a 60 degree bank you are in forward flight and you have the benefit of translational lift. Plus, you're more than a few feet off the ground !
Hover performance is marginal in an R22 at best when close to all up weight, let alone over it ! Even at sea level you could find yourself struggling to get a decent hover, then it'd be all too easy to overpitch it, or catch a skid and roll the whole thing over.
Hover performance is marginal in an R22 at best when close to all up weight, let alone over it ! Even at sea level you could find yourself struggling to get a decent hover, then it'd be all too easy to overpitch it, or catch a skid and roll the whole thing over.