Exceeding maximum gross weight [Archive]

Senior Pilot

3rd Feb 2010, 19:50

I can't help but reflect on how times (and attitudes!) have changed: Bristow operations (http://www.pprune.org/5488942-post1160.html)

Performance in accordance with the Flight Manual was not really practical ; the pilots stuffed the aircraft with as much fuel as they thought they could carry often departing 300lbs over max gross weight. If necessary the ship was turned to give a relative wind of 45 degrees port or starboard. On the deck the rotor blades were lower than the level of the life boats and davits, which had to be cleared on lift-off. The technique in these piston engined machines was, after cockpit checks had been completed, reduce rotor RPM to ground idle for a few seconds then increase throttle and power, lift off and go, making as little cyclic and pedal inputs as possible. Having cleared the deck dive toward the sea to build up speed and translational lift and you were on your way.

:eek:

:hmm:

Dantruck

3rd Feb 2010, 20:34

To truly include all adverse factors be sure to include the Law of Unintended Consequences.

It states: There will always be unintended consequences.

At worst, in helicopters, this means the next poor sod and all his pax die a horrible death on what should have been a gentile and lovely pleasure trip because you failed to log that last over temp start or all those over-torque T/O's, et....etc... etc...

Now! Who among us can stare the keyboard in the face and say: "Never I, Dan" ??? :uhoh:

Metal does indeed have a memory. Never forget, fellow pilots, every bearing, tail rotor blade and pitch link knows what you have previously asked of it. That component cannot speak to the investigator, but that is exactly why we have Tech Logs.

If you can't understand the above you have no business in a cockpit.

Dan

PS:
You know what really pisses engineers off? It's those idiots in the pub who tell you it is legal to drive 15% over the speed limit because there is a tolerance on car speedometer accuracy that permits that much error? They can't quite grasp that instrumental error is granted to the instrument maker...not the driver. :ugh:

Dan
(and for those wondering, no, car instrumental error is not a permitted 15%)

topendtorque

3rd Feb 2010, 20:42

That is a very valid point Senior pilot.
One only has to read the old australian army handling notes for the souix and you will see that it is recommended to run the RPM 100 over the the red line for those same sort of departures.

So it is not much wonder that many of us engaged in these over loading type maneuvres way back when we were flying aircraft that were NOT designed to closer tolerances and thus shorter real life by computers. The '47 blade for example was built like the provervial brick turnout.

Jumping helicopters off the ground was a trait often used, but still deplored by many even back then and it was the reasson that many people were killed, particularly in New Guinea, I.e. hot high.

Jerking the collective up was one thing, but getting yourself to an area where you could then push it down again to recover RPM was a real issue.

we certainly spent lots of time teaching people to only allow the A/C to be loaded so that it could be capable of climbing under its own merit.

Even the confined area take off technique that I and many were taught we don't teach operationally any more, certainly not to any one with less than quite some hours, as it is too risky for a miscalculation. I.E going smoothly from light on the skids to full power and immediately setting the angle of attack for the airspeed which gave you the "highest angle of sustained climb". one major problem was the before take off checks to (hopefully) ensure that the turbocharger was going to spool up for you.

which they often didn't on a hot day and the first start up at say 11.00 am after you have been collecting samples.

Brian Abraham

4th Feb 2010, 04:08

One only has to read the old australian army handling notes for the souix and you will see that it is recommended to run the RPM 100 over the the red line
Interesting TET. Recall a crash comic telling the story that many of the engine failures in civil 47's in Oz were the result of overspeeding that produced valve bounce. Engine failure due to dropped valve occurred some 25 hours later. Wonder if there may have been some misunderstanding of the Army technique as a result of grapevine talk (ie using more than 100 rpm), or alternatively perhaps representative of a "she'll be right Jack".

bellfest

4th Feb 2010, 05:10

I reckon you would probably need more than an extra 100 RPM to valve bounce a 435 in a 47......... I think those overspeeds were more to do with pilots having a fast left elbow and a slow left wrist!!

topendtorque

4th Feb 2010, 10:53

crash comic, yeah well don't believe everything that your read in a newspaper they say. although in recent years there seem to be less lapses of the imaginery and ridiculous.

Valve bounce speed will be reached following a freewheel failure. The noise is frightening, the fan throws the belts and i don't know what RPM it is but it definately stopped accelerating before i got the throttle off in a heartbeak or well less. overspeed checks did not yield anything unusual, but in strip down it was a different story.

There was another twist to it which I won't relate.

The rest was is as bellfest says, finger trouble. over 250rpm over usually rewards the engineers with some metal sample at the 75 to 100 hour mark afterwards depending on the power pulled at the time.

i remember being told to go to 3400 and bleed off if I was real stuck, which I was in a 3B2 once. The task was to lift out a crashed 3B1 from high timber at fairly high DA. we did it in two lifts.

on the second trip we loaded the litters and the hook load and left it there while I dropped the gingerbeer at a clearing about half a mile away.

Loaded with the gingerbeer his tool box and the hooked load, ect. I went to 3400 for about two seconds as we climded towards 35.5 (one inch under max for temp correction on the day) inches, and i felt I could feel the metal shredding. I gave that away and bounced it off instead from 3300 and just as we got around the corner the gingerbeer nearly sh*t himself.

right there only fifty yards from where he was were about ten very curious wild buffalo. we didn't stuff the engine, but oh so close i think.

rotarywise

4th Feb 2010, 23:34

Having cleared the deck dive toward the sea to build up speed and translational lift and you were on your way.Ah yes, with nothing more than an Alvis Leonides between you and the oggin. Happy days, although we might have been more confident if the bl**dy engine could have been started without the need for a liberal beating with a chock!

Brian Abraham

5th Feb 2010, 12:47

crash comic, yeah well don't believe everything that your read in a newspaper they say. Yeah well, I learnt not to believe a lot of what a chief pilot or CASA had to say either.

I must say I'm impressed with the advice to spin it up to 3400. How does that comply with the requirements of CAR 138. What dispensation did you have, it seems indicative of the pervasive cowboy nature of helicopter ops IMHO.

If I seem hard nose, let me explain. On a beautiful tropical morning we launched at 0600 with a flight of five Hueys to an airstrip some distance away to conduct combat assaults. I was tail end charlie (#5) and following refueling and shutting down at the strip, I was engaged in conversation with #4. He complained about certain problems with his aircraft and I volunteered to fly in his place, as the mission had only called for 4 aircraft, and I and my crew had been put on standby. He was adamant that he would fly the mission. I could very well have pulled rank and told him that I would fly in his place, but I respected his abilities, as we had been through some tough times together, and let him have his way.

While basking in the sunshine following their launch for the CA we saw the C & C aircraft come into POL, which was unusual as the flight usually landed well before C & C. C & C landed at POL and a figure could be seen walking down the airstrip towards us at the opposite end of the strip. I walked up the strip to meet him half way to find it was our CO in tears. #4 had crashed with the loss of all on board, 4 crew and 10+ pax. There was an official finding to the cause, but with my conversation with the AC prior to the flight I have a fair idea to the real cause, which is at complete odds with the official finding.

It is somewhat mind concentrating to stand along side a Huey, the top of which reaches your throat, the interior painted red rather than the military grey, and picking pieces of nomex containing flesh off bolt heads.

http://i101.photobucket.com/albums/m56/babraham227/n0003.jpghttp://i101.photobucket.com/albums/m56/babraham227/n0004.jpghttp://i101.photobucket.com/albums/m56/babraham227/n0005.jpghttp://i101.photobucket.com/albums/m56/babraham227/n0006.jpg

RIP guys, very few appreciate what we went through and did.

topendtorque

6th Feb 2010, 23:46

it seems indicative of the pervasive cowboy nature of helicopter ops IMHO.

Yes there’s no doubt that there will be a certain cowboy attitude creep into – “high volume hours with not a great amount of hindsight experience situations”

I’m guessing that was the problem with the accident which you reported. What is it that you despair about? Not flying the mission yourself and sending the other A/C home, almost certainly still to an untimely end of flight even without its load, or the experience that you may have gained since which would tell you that an A/C which was developing an unexplained lateral or even vertical was an ironclad reason to ground it and send for the engineers?

We found that, and especially an increasing lateral when investigated would yield such unpleasant discoveries such as cracked masts. Now the rule is, - never fly with an increasing lateral. We have since found that blades on A/C which are difficult to track and inconsistent in the vertical plane also is reason to ground the aircraft. No doubt the catastrophic blade failure near Warragamba dam accident will refresh your memory there.

In our case we had studied the over speed engine and airframe check procedures and figured prior to this event that we were on safe ground. My event made us believe that we weren’t. In fact we figured later also that most of the power required to spin up to 3400 was used in doing just that, leaving little for the use of lifting. I even managed to prove that with the difference between 3300 and the red line of 3200. We were on the way to finding the most efficient blade RPM/engine power combination. It was not just a limitation imposed for the health of the engine. That is why we now teach as I stated before, to hold it at the red line and only load it to Max AUW as any a/c with an engine operating in specs will lift vertically its own Max AUW up to its hover OGE ceiling in free air, I.E. not close to trees .

Think about it, that is always a revelation to newbies straight from flight school, and many others and can be easily demonstrated.

If that is the case why on earth did the oz army adopt the cowboy attitude of fragrantly breaching CAR138 with their precious recommendation of exceeding the allowable RPM?

My referral to the crash comic is about an accident where the it stated that “the accident was caused by T/R failure”, when in fact both of the tail rotor blades had been torn off, and one of them flung at least 150 feet through light brush when they had contacted the ground. You would have to admit there is a major problem with that abhorrently fragrant “trial by media” supposition. Particularly, as the accident is still awaiting the pleasure of the coroners’ attention, for seven years now. It sounds to me that you are close to the ATSB action, perhaps if you’d like me to PM you the accident report number and you might look into it.

The beauty of these forums is that we can pass on gems to newbies.
They have been lucky to pick up a few from this one all of which relate to a single regulation, (CAR 138) that I’ll bet most have never been introduced to.
cheers tet

chopjock

7th Feb 2010, 10:32

Of course you may still lift "overweight" and not have any "Adverse Factors", for example use a technique that gets you airborne without exceeding the engine limitations. (for example a cusion creep at sea level on a cold, windy day in an open space and a very shallow climb out). Also consider this, even if you lift at the MGTOW, you can still simulate being over weight by climbing too quickly. ie rotor head pulls max weight upwards,(within limits) which dynamically adds weight during the climb.
So it makes me wonder, lift at MGTOW, climb out steeply within engine limitations, is probably a similar airframe stress to lifting at over MGTOW and make a lesser best rate of climb within engine limitations.

Fareastdriver

7th Feb 2010, 13:28

In the late seventies the offshore oil industry used much the same rulers as routine civil air transport. Male passengers weighed 170lbs, female 140lbs. You would plan your flight taking on the max amount of fuel as possible depending on the pax and freight. The manifest would arrive with nineteen pax at 170 lbs each. After start nineteen overweight gorillas, each at least 200lbs, would tramp out to the aircraft. 19X30=570lbs overweight to start off with. A whole generation of Pumas and S61s did not seem to suffer.

Going further back. The only way to check the power settings of turbine powered Whirwinds and Wessex was to run them on a tie down base. Here the aircraft were strapped to the ground on a specially built pan that had steel retaining rods set in the concrete. Some of the coning angles that the main rotor achieved setting full power were tremendous and all the strain was taken up by the gearbox mountings. Again they did not seem to suffer.

Years ago I had to carry out a check on an engine that had had a compressor stall and had cooked the turbine. There was no tie down available so we had to use human weight. It still got airborne with everybody inside at full power.

http://i229.photobucket.com/albums/ee224/fareastdriver/WhirlwindTiedown.jpg

The problem with being over weight is not so much getting airborne but in forward flight. The aircraft has a VNE for a certain weight, you go above that weight and you have no idea what the VNE for your new weight is. Your rotor head will know because of the stresses that are building up by you flying in excess of that unknown VNE. One occassion that I remember a certain pilot used to ignore things like MAUW and VNE, full power was his only datum. He unknowingly overtook his flight commander and then the truth came out. They replaced all the rotor heads on all the aircraft he had flown.

All pilots will at some time or the other get airborne overweight, either knowingly or otherwise. Grotesquely overweight you bring it back at a reduced speed so as to look after the head. As a small percentage of your permissable weight fly it at a reduced speed until it gets down to MAUW. and then just carry on. As a rule of thumb if by continuing your flight it is going to take less time to get your weight down than by turning back then carry on.
A lot of the weight limitations are certification issues. The S76, for example, started off at 10,000, grew to 10,300 and then to 10,800lbs. I do not recall any S76 falling out of the sky because they were too heavy. The 332L is limited to 8,600 Kg, that is so it can meet various performance criteria. Ferry flights are exceptions and so are USL operations were you can go to 9,100 kgs all day as long as you can jettison your load.

I can visualise the barrack room lawyers and holier than thou brigade banging their flight manuals but these things happen. It stood me in good stead for 44 years and 18,000 hrs.

Jack Carson

7th Feb 2010, 14:05

Don’t confuse evolutionary weight increases with operating outside of an aircraft’s published weight. The S-76 is a good example. Each evolutionary growth in weight was a planned, designed and certified as a growth version of previous models. The gross weight increases were accommodated for with structural beef ups and an increase in operating rotor speed to provide the required lift. Similarly, the MH-60K, a growth version of the Basic Blackhawk, operates at increased gross weight form the basic model. It this instance the dynamic components of the MH-60K are identified and tracked separately. The MH-60 component lives are significantly reduced as a result of this higher gross weight envelope.

Jolly Green

7th Feb 2010, 22:32

I think others on this thread have commented adequately on the possible power limits of flying over gross. The problems develop more insidiously if the power is adequate for near normal operations over maximum gross weight.

The USAF flew it's H-53 fleet over gross in the late 80's and 90's for a variety of operational reasons after the fleet transitioned from the rescue to the special operations mission. Unfortunately for us we did it backwards from the S-76 fleet. We did it, and then told the certification authorities what we had done. They came up with an inspection regime and then we'd go off and do it again. Not real smart on our part, I'll admit, but we never lost an aircraft to over gross operations.

Real problems happen when you operate off the charts. Working with extropolated charts worked fairly well for us for engine power and hover performance, but we were somewhat surprised after the engineering got done that we had also been operating out of permissable cg limits. The aircraft did crack where the engineers thought it would. It also cracked bent and wore out in places they didn't expect.

If lives don't require you to fly over gross, I highly recommend you don't do it, because lives are at risk when you do.

bvgs

8th Feb 2010, 15:25

I just wonder how they work out the max weight? For example if you fly 50lbs overweight in say an R44, however are flying in a straight line are you not puting less strain on the various components than if you are at max weight and doing lots of banks and turns. So I wonder how they come up with the figure. I doubt if an R44 flew continual figures of 8 at 60 degrees that they would ever reach 2200 on the appropriate components. It tends to suggest that somewhere someone is puting their finger in the air and using the laws of average, perhaps thats why many pilots do fly overweight, thinking they can get away with it:=

Fareastdriver

8th Feb 2010, 21:00

As soon as you turn an aircraft you increase the load on it's lifting surfaces. The rotor system would read this as increased weight that it has to counteract. In level flight it is 1G so the rotor is supporting the actual weight.
A thirty degree level turn produces a loading of 1.17G. An aircraft weighing 5000lbs now weighs 5850lbs.
A sixty degree level turn produces a loading of 2G, it is now 10,000lbs.

An R44 would manage the first but unless you are flying a powerful multi-engined helicopter at about 70knots you would be pushed to achieve the second.

MightyGem

8th Feb 2010, 21:07

Or an Army Air Corps gazelle. 60 degree turns were a regular exercise.

bvgs

9th Feb 2010, 08:58

So......flying 60 degree or even 30 degree turns makes the helicopter technically overweight for the duration of the turn but thats ok as you are within the max weight at take off. It therefore must be correct that flying slightly overweight in a straight line puts less strain on the heli than flying within weight through terrain that requires lots of banks/turns. So I'm still wondering how they work out the max weight with such variable forces?

Jack Carson

9th Feb 2010, 14:09

In the US, the military and the contractor cooperatively develop a usage spectrum for each aircraft. This spectrum is developed about a design gross weight, not the aircraft's actual gross weight. I believe the Blackhawk design weight is approximately 16800 lbs and the CH-53E was approximately 48,000 lbs. This developed usage spectrum includes operating scenarios about this weight, including time above it. A percentage of total flight operating time is assigned to each element of the spectrum. As an example:

5% - level cruise at best range
0.5% - Cruise at Vh
1% - 30° bank at best range cruise

These very detailed lists are then used to compute component lives for the aircraft. There are many instances where operational requirements change and the list has to be revisited and component lives are recalculated. The previously mentioned MH-60K is one example where the time spent at higher gross weights required a recalculation of the components lives for that specific model. I hope this helps. Maybe John Dixon can weigh in with more specifics on the Hawk.

FauxZ

9th Feb 2010, 15:36

I'd assume that G loading is part of the design process, I wish I could say what it was, but I don't have the data. But I'm sure the ship has to meet some figure like "safe for all loads below 3G's" or something similar.

I know that's how things go in the airplane world. Again, I don't have the inclination to look up the numbers now, but I'm aware of some air planes which have different categories based on their GW. Example, if you load the ship to 3000lbs, it's a Utility ship, which says it's certified for 5G's of stress. However, if you choose to use 3500lbs as a GW, you're limited to Standard category which may only be 3G loads (bank, maneuvers, etc.)

Anyways, the point I'm trying to make is if you could guarantee the ship would never see more than, say, 1.2G's, without any turbulence, under maximum maneuvering speed, then you would cause no damage beyond increased wear.

Of course, heli's don't always list "max maneuvering speed," you can't ever guarantee you won't exceed 1.2G's, or encounter any turbulence, and the ships were designed with these G loadings more as a transient than a continuous load.

Really though, as others have said, this is all moot. If you fly it over gross, and are caught doing so, the blame for future or current failures will most likely lie on you from the eyes of the victims, employers, and insurers.

JimEli

10th Feb 2010, 04:37

Simply stated, maximum gross weight is used to determine component strength and service-life, and rarely has anything to do how much a helicopter can lift.

Unlike fixed-wing aircraft, it’s virtually impossible to design a rotary-wing aircraft using “fail-safe” principles, especially when it comes to dynamic components. For example, try designing a fail-safe pitch change rod. Therefore, helicopters use the design philosophy of “safe-life” components. Safe-life uses the methodology of designing components in such a manner to prevent fatigue failure while in-service. The 2 fundamental elements to safe-life are strength and service-life (time). Generally speaking margins are applied to both elements, however if either element is exceeded, the ultimate result is potential catastrophic failure--maybe not while you’re flying the helicopter, but possibly for the crew after you.

chopjock

10th Feb 2010, 08:53

Therefore, helicopters use the design philosophy of “safe-life” components.

As well as "on condition" components, which usually last proportionally to how well you treat the aircraft. You can still overload the aircraft and then fly it gently and not have any ill effects, in my experience. :ok:

GoodGrief

10th Feb 2010, 09:16

. You can still overload the aircraft and then fly it gently and not have any ill effects, in my experience. :ok:

I think that smiley is inappropriate, but maybe that's just me.
You seem to be very experienced as a test pilot.

I have seen an owner/operator cry seeing the bill for the prematurely overhauled transmission.
His credo was:"She's an L3, she'll lift it..."

chopjock

10th Feb 2010, 10:39

You seem to be very experienced as a test pilot.No But I have owned an Enstrom for over 17 years and put about 1500 hours on her. In the summer there is not enough power to take off much over weight. However when it's cold the power available allows more performance and taking off over weight can be done easier. I absolutely keep her within the power limitations though. When I add a smile :) it's because I'm happy with that statement. :)

I have seen an owner/operator cry seeing the bill for the prematurely overhauled transmission.

I'm not sure though why you would overload the transmission if you stay within the power limitations.

GoodGrief

10th Feb 2010, 10:46

Chopjock,

did you just forget to switch on the irony button or are you just pulling everyones leg?

Could you really be dumb enough to publicly state that you constantly violate rules and regs?

Re-read Jack Carson's post #6.

ShyTorque

10th Feb 2010, 10:53

No But I have owned an Enstrom for over 17 years and put about 1500 hours on her. In the summer there is not enough power to take off much over weight. However when it's cold the power available allows more performance and taking off over weight can be done easier. I absolutely keep her within the power limitations though. When I add a smile it's because I'm happy with that statement.

You are happy with that statement? I think you might be alone in that view.

For example, how do your insurance company, the manufacturer, your maintenance company and the CAA feel about it?

chopjock

10th Feb 2010, 12:50

Could you really be dumb enough to publicly state that you constantly violate rules and regs?
Never stated anything like that.

how do your insurance company, the manufacturer, your maintenance company and the CAA feel about it? Insurance company don't want to know unless I have a claim.
The Manufacturer don't want to know unless they are consulted.
The maintenance co. would only be informed if I exceeded Engine limitations etc.
The CAA do not need to be informed unless there is an accident. If I ever broke the ANO I would not ask the CAA how they feel about it.

Does everyone on here weigh their pax before flight?
Is anyone here 100% positive they have never ever taken off over weight?

Bravo73

10th Feb 2010, 16:04

Gents,

I really wouldn't bother wasting your time with chopjock.

I suspect that he's just a troll. The majority of his comments and opinions on this site seem to be inflammatory in one way or another. I suspect that he just says these things in order to illicit a reaction. Classic troll behaviour.

B73

Gaseous

10th Feb 2010, 17:58

CJ
The problem with exceeding max weight is that there is no way of knowing what, if any effects there will be on the aircraft. Enstrom use many common parts across the range with different maximum gross weight limits. Some of these parts are lifed the same across the range, others are lifed differently or have different inspection schedules. Clearly Enstrom set these parameters for a reason. Going over limit is unlikely to cause any problem in the short term but is russian roulette in the long term because you cannot predict what will fail or when - if anything. The chances of failure are probably slim but you cannot know the full risks.

Do yourself a favour. Buy some scales, if theres any doubt, weigh the pax, calculate your fuel and endurance. If the sums dont add up, dont do it unless someones life depends on it.

Do I weigh them? - Yes if it looks even close.

Edit: check out the life of the main rotor hub plates on a 280 and a 480 - same part, drastically different life.

ShyTorque

10th Feb 2010, 19:31

Chopjock, You say you don't violate rules and regulations. However, if what you have posted is correct and you are for real (which I do doubt), by operating it overweight you invalidate the C of A of your aircraft and therefore also your insurance. You also compromise your maintenance company, especially the bloke who last signed the aircraft off as serviceable. Believe me, they take that sort of thing extremely seriously.

If you do have an accident, your insurance company will probably deny liability and it would be left to you as an individual, or your estate, to pay damages. I for one don't relish the thought of a wife or kids losing their house over something totally avoidable.

chopjock

10th Feb 2010, 20:25

What's the difference between these following examples:

1) Lift at MGTOW and climb out at max performance OAT 15 deg.C and obtain 1600 fpm rate of climb, then cruise at MCP and achieve 85 kts straight and level.

2) Lift at 150 Lbs over MGTOW and climb out at max performance OAT 15 deg.C and obtain only 1000 fpm rate of climb, then cruise at MCP and achieve only 80 kts.straight and level.

3) Lift at 150 Lbs less than MGTOW and climb out at max performance OAT 15 deg.C and obtain 2,000 fpm rate of climb, then cruise at MCP and achieve 90 kts straight and level.

As far as the engine and airframe are concerned, the strain on the rotor head is the same, is it not?

tony 1969

10th Feb 2010, 20:43

Chopjock quote
"What's the difference between these following examples:

1) Lift at MGTOW and climb out at max performance OAT 15 deg.C and obtain 1600 fpm rate of climb, then cruise at MCP and achieve 85 kts straight and level.

2) Lift at 150 Lbs over MGTOW and climb out at max performance OAT 15 deg.C and obtain only 1000 fpm rate of climb, then cruise at MCP and achieve only 80 kts.straight and level.

3) Lift at 150 Lbs less than MGTOW and climb out at max performance OAT 15 deg.C and obtain 2,000 fpm rate of climb, then cruise at MCP and achieve 90 kts straight and level.

As far as the engine and airframe are concerned, the strain on the rotor head is the same, is it not?"

The strain may well be the same, I cant see it standing up in court though.

Surely by that argument "I am not speeding officer because I was driving up hill and therefore I have to use the brakes less if I need to stop !"
:}

ShyTorque

10th Feb 2010, 21:07

As far as the engine and airframe are concerned, the strain on the rotor head is the same, is it not?

Why do you think it is? The only sure way is to ask the manufacturer, to see if such tests have been done. They set the operating limits for their aircraft. Once you go outside those limits, you're a test pilot.

Note that test aircraft are wired for data logging using strain gauges etc, and are far more deeply examined than yours is, after every flight.

The real answer is, they possibly have, in the past, explored a wider performance envelope. If they could safely certify a wider performance envelope, they would do so because it makes commercial sense to do so.

But they haven't, so go figure why not.

Would you treat your car like this? Routinely exceed the rev limits, for example, just because you can get it to rev higher than the red line?

I still think you're not for real.

chopjock

10th Feb 2010, 21:29

Stand on a scales in a lift. You will weigh more going up than coming back down!

Max weight on a heli is directly proportional to how much strain is applied to lift it.
If you limit the amount of power to lift it with, then you are also limiting the stress to that same limit. My point is overloading a heli and flying within the power limitations is not the same as overloading a heli and then flying it normally, exceeding power limitations to get airborne, this is what causes the damage.

How often has anyone strapped a heli down and loaded it up with weight so that it will not be able to take off, in order to perform a max power check? This would be clearly over weight, but would it invalidate the C of A? I think not.

212man

10th Feb 2010, 22:06

Stand on a scales in a lift. You will weigh more going up than coming back down!

If that's the level of your knowledge of physics, I'd give up arguing now!

ShyTorque

10th Feb 2010, 22:24

Stand on a scales in a lift. You will weigh more going up than coming back down!

:D :rolleyes:

Jack Carson

10th Feb 2010, 23:34

I agree that we may have a troll looking for an argument. Only one thing needs to be understood. Limitations are just that, limitations. Why they have been identified as limitations (i.e. gross weight, airspeed, engine power or maximum certified altitude) are not for us to question. It is not ours to attempt to determine why a limit has been imposed but rather to obey it.

Once, in a former lifetime, I was assigned with the task of evaluating the autorotative performance and flying qualities of the CH-53D at the aircraft’s forward and aft CG limits. As part of my preflight preparation I contacted Sikorsky for advice when approaching the limits in this evaluation. Their advice was simple and direct. Be careful and don’t exceed the limits.

Brian Abraham

11th Feb 2010, 01:15

Limitations are just that, limitations. Why they have been identified as limitations (i.e. gross weight, airspeed, engine power or maximum certified altitude) are not for us to question.
Unfortunately Jack there is a belief in some quarters they are only advisory, because there is a built in safety factor yada, yada. Like an R-22 operator, who I'm sure would have been surprised had he lived, that flying the blades beyond their retirement life was not a good idea (but, but, the safety factor yada, yada). You wonder why manufactures go to the expense of employing engineers who spend their time crunching numbers to ten decimal places. Just send a questionnaire to XXX number of pilots and get their opinion as to where to place the yellow, green or red marker. Much cheaper. :ugh:

Saw the result of a Hughes 500 that lost it's head as a result of doing aerobatics. Unfortunately the two guys flying it at the time were not the ones who had performed the aerobatics. Manufactures don't go to the trouble of printing the AFM in order to,
(a) consume forests
(b) keep people employed
(c) move the CofG forward.

It's to keep your sorry ass in one piece.

valve guide

11th Feb 2010, 01:44

Anyone fancy buying Chopjock's Enstrom..........................................Really?

JimEli

11th Feb 2010, 02:27

A few things to consider (found in FAR part 27 and other sources):

Strength requirements are specified in terms of limit loads (the maximum loads to be expected in service) and ultimate loads (limit loads multiplied by prescribed factors of safety). Unless otherwise provided, prescribed loads are limit loads. A safety factor might only be 1.25 or 1.5--we don't fly tanks, we fly lightweight aircraft.

The rotorcraft must be designed for--
(a) A limit maneuvering load factor ranging from a positive limit of 3.5 to a negative limit of -1.0; or
(b) Any positive limit maneuvering load factor not less than 2.0 and any negative limit maneuvering load factor of not less than -0.5 for which--(1) The probability of being exceeded is shown by analysis and flight tests to be extremely remote; and (2) The selected values are appropriate to each weight condition between the design maximum and design minimum weights.

+2.0g!

The rotorcraft must be designed to withstand, at each critical airspeed including hovering, the loads resulting from a vertical gust of _only_ 30 feet per second.

The speed for maximum load factor capability for a helicopter is approximately 0.6 Vh--not Vne/Vdl.

As flight speed increases, a given rotor angle-of-attack change produces a larger thrust increment so that large load factors may be reached without large attitude changes. The maximum loads thus may be obtained by variation of rate of control application, magnitude of control movement, and speed.

The maximum power-off rotor speed limit is essentially the design limit of the rotor (with some reduction for a factor of safety). Thus potentially much higher rotor load factors can be generated under autorotation than powered flight.

Landing gear have limitations too.

topendtorque

11th Feb 2010, 12:55

Let's see now, up up in the lift, the blood goes thin,
down down in the lift I feel a thickness near my shin.

damm it, there you are all, the same as lifting off in the ol' flying machine and getting light headed, and well - then going back down again and landing and trying not to look too thick! all with the same persistant writing in section two - Limitations - oh well.

I guess that destroys that argument there chopjock ol' son.

but I think Brian Abraham crystallized it for me when he labled Jock as Jack.
No I don't tink so Brian, Jack is still be on the way UP the hill with Jill. jock is beyond the pail and is cometh tumbling down.

all the best jock ol son.
tet

chopjock

12th Feb 2010, 09:06

The rotorcraft must be designed for--
(a) A limit maneuvering load factor ranging from a positive limit of 3.5 to a negative limit of -1.0; orWell if the min requirements for airframe design are to withstand +3.5G, then lifting at 1.05G, whilst remaining within Engine (Map, rpm, cyl head temp etc) limitations can hardly over stress an airframe. Especially when the likes of Dennis can pull out at 2 G at the bottom of a stall turn. (Does this weight of 2G invalidate the C of A, I think not)

Anyone fancy buying Chopjock's Enstrom..........................................R eally? v g, are you suggesting I have overstressed my airframe somehow? She is well maintained and I can honestly state I have never red lined her.

valve guide

12th Feb 2010, 14:32

You simply have done what you shouldn't have done......period! Lets just say that you replaced your piston engine with a turbine of the same weight but with bags more power, would you think it ok to load up the heli, well overweight as long as you weren't exceeding the "engines" limitations. If you are selling it don't advertise under chopjock or a very difficult machine to sell will become impossible.

Might be worthwhile to publish your registration so we can all follow it and be proved wrong as the years and hours go by. Haha like you would do that......I don't think so!!!!!!

Shawn Coyle

12th Feb 2010, 15:38

Chopjock:
You're way out of your league in terms of talking of limits and designs. There is a maximum weight published in the limitations. Your job is to not exceed it.
Ignorance is not excuse in a court of human law, nor in the court of physical laws.
(I was a certification test pilot for 5 years for Transport Canada, and can testify that there are a myriad of reasons for weight limitations, as well as other limitations.)

nigelh

12th Feb 2010, 15:42

Chopjock .....you are not giving the EOGOC a good name you know :ugh: I think the point is ....going slightly overweight as a genuine mistake is one thing , ( we have all asked for 150 ltrs only to find 200 put in or a girl turns up with a handbag the size of a suitcase ) , intentionally going over is another . What happens when you allow yourself that extra 100lb you shouldnt have ....and then you "just" go say 25lb past that new limit you have set ?? Where does it stop ? It is pointless saying most of us never do it , ever ...but it is a bad thing to get into a habit and equally bad to flaunt it !!

ps I used to consistently massively overload Bell 47,s spraying but they have all crashed now so part life not so much of a problem . ( also people were not mostly v sensible 30 yrs ago !! )
pps EOGOC Enstroms Old Git Owners Club.

chopjock

12th Feb 2010, 17:51

You again miss the point. What about your landing gear, for just one thing? You have stated you've operated your machine outside its design limits. Period.You are "putting words into my mouth" again. Read my posts, I never stated that.

I'm making a point, and that is if you load up to max weight and climb at max power, it's no different than loading 5% over weight and climbing at the same power. (this doesn't mean I've done it though)Your climb rate will be lower, but the strain on the airframe will be the same. I'm not asking for approval or even your agreement. Just stating a point of view. Jeez :ugh:

Phil77

12th Feb 2010, 20:39

You are "putting words into my mouth" again. Read my posts, I never stated that.
:confused:
You can still overload the aircraft and then fly it gently and not have any ill effects, in my experience.If I may pitch in, with english not beeing my first language and all...
how could I possibly translate "in my experience" differently as "I have done it"?

Definition:
experience |ikˈspi(ə)rēəns|
noun
practical contact with and observation of facts or events
• the knowledge or skill acquired by such means over a period of time, esp. that gained in a particular profession by someone at work

chopjock

12th Feb 2010, 20:55

If I may pitch in, with english not beeing my first language and all...
how could I possibly translate "in my experience" differently as "I have done it"?In my experience I have seen many an Enstrom grunt off in the summer, three up and full tanks of fuel, marginally managing a positive rate of climb, within power limitations, but slightly over weight. (I was one of the pax). In my experience, I have also seen many an Enstrom grunt off in the winter, three up and full fuel with a spring in it's step, still within engine limits. The fact that I have seen this, would suggest that I have experienced it.:rolleyes:

Jack Carson

12th Feb 2010, 23:31

It is not approval that is required to argue this position. I also submit that to operate a flying machine outside of its certified envelope is arrogance and with no malice intended, stupid. Like many on this site I have many years of rotary wing flight experience in many machines, including flight test and certification work. This knowledge and experience has provided me with a solid understanding of the design and certification of rotary wing aircraft. The only way that the longevity and safety of a vehicle can be assured is to operate and maintain it within the guide lines out lined in the appropriate manuals. To do otherwise is not smart. I can state this with confidence as one that signs my name to the posts on this site.

tony 1969

13th Feb 2010, 08:07

chopjock
Why do you consider its acceptable to exceed weight limitations but not acceptable to exceed engine limitations ?

chopjock

13th Feb 2010, 08:59

chopjock
Why do you consider its acceptable to exceed weight limitations but not acceptable to exceed engine limitations ?I have not said I find it acceptable to exceed anything. I have given my opinion on what happens if you do. And if you remain within your power limitations, nothing.

ShyTorque

13th Feb 2010, 19:19

Chopjock, you obviously misunderstand some issues.

Helicopter critical component and airframe fatigue life is calculated in cycles, at no more than the certified max weight. If you routinely exceed the maximum weight, there is a cumulative effect, an unknown and possibly very serious one, and we're not talking about engine life here.

I strongly suggest that you fly the aircraft in accordance with the manufacturer's limits because from what you have written here you are compromising yourself, and others, in more ways than one. Speaking as someone who has been flying for a living for over thirty years I, for one, would not now fly in your helicopter at any cost. Unfortunately, because I don't know who you are, I would now be very cautious of ANY Enstrom, in case it has been flown by you.

nigelh

13th Feb 2010, 22:44

SHY lets not go over the top here . You would not find a single Bell 47 that hasnt been put through overloading in its life ...anywhere !! I see your point but i think this is becoming a bit od a witch hunt . If he has been slightly over in the past i would sugggest that his machine is thoroughly investigated and he doesnt do it any more . I think you can tell by his posts that he realises it isnt big or cool to do it . All professional pilots know that flying a helicopter is a bit like being with a girl ...ie her past history may come back and bite you :{ so we all have to respect the machine we are handing over to the next guy .

ShyTorque

14th Feb 2010, 00:00

nigelh,

You have just repeated and agreed with the main gist of what I had written!

However, as some of us do know, nothing seems 'OTT' compared to a major component failure on a helicopter. One esteemed poster here tragically lost his son to a helicopter accident. I've also lost enough friends and colleagues to aviation accidents over the last thirty years (including my closest friend) to understand at least some of the resulting issues.

On the 11th October 1979 I came very close to having it happen to me when a MRB departure was found to be immediately imminent from our aircraft, due to terminal metal fatigue of the main spar. Thankfully we were safely on the ground when the full implications of what would have occurred a few minutes later were realised. The groundcrew were horrified at what was found, so were we. The main 'D' spar was cracked through, all but for the "nose", an area not much bigger than a ten pence piece; this was on a 7 tonne helicopter. Apparently the crack had spread very rapidly, probably all of it on our 45 minute sortie. Less than five minutes before we had been flying at 140 kts.

However, as my comments are seen as OTT, so be it; I'll participate no more after this, especially as it's actually easier to keep well intentioned advice to one's self.

EBCAU

14th Feb 2010, 01:10

I have come from a background where a culture of loading up to whatever the machine will get off the ground with was the norm. Indeed, if you didn't you would not have a job for long! It never seemed to be a problem way back then.

On board weighing systems weren't available in those days. It was an eye opening experience when I got to fly with one of these devices. As soon as you commence a turn, take a look at the scale. See what a load it's become! A small percentage overload becomes a big one once you get angles of bank involved.
I'll let the physics experts, and those that sat Principles of Flight exams more recently than I, explain how that works.