Center of Gravity?

[pilot#476398]

Since we're already on this, I thought I'd delve a little deaper. Most CFIs I've flown with just do some quick addition in their head to make sure we're under max gross weight,...but none of them ever seem to check if we're in balance or not!

 

I know from experience that in an R22BII if the pilot + the CFI = around 400lbs (sometimes a bit less) that the forward CG will be just over the line. Since the Robbie CG envelope shrinks as you go from 1275 to 1370 (I knew that from memory,...suck on that CFI who didn't know the fuel capacity in his 44! ) as you add fuel your CG will stay beyond the forward line, so your situation will not improve!

 

This situation will happen even though you are under max gross weight!

 

So, how many of you have flown an R22 like this, because you didn't check the "balance" part of the "weight & balance"?

 

How many of you check the CG at all?,...especially you tour guys?

Edited May 6, 2013 by pilot#476398

[DS_HMMR]

That hypothetical W&B would be every training flight I ever did in an R22. My first CFI never shared his true weight with me until well after I had concluded my training. He "let slip" one day about having to lose weight in order to get a job flying Astars in the ditch. When he told me how much weight he had to lose, I realized that I had done all my private pilot training (minus a little R44 time) way over max gross, and out of CG.

[DieselBoy]

from experience

 

You said it. When I start flying a new aircraft I play with the numbers to figure out my limits. 135 Operators will have a Load Manifest.

[pilot#476398]

The funny thing is that, that thread on "Exceeding Max Gross Weight", reminded me of another thread which asked about being too heavy to be an R22 CFI. Some posts on that one were from pilots claiming that at around 200lbs they flew with students/CFIs weighing 200lbs or more (one even said 235lbs!), "so don't worry about it, you'll be fine". It just made me think, they may have been ok with regards to MGW, but I'll bet they were out of CG!

 

When I did an intro flight in an S300, way back when, I asked the CFI if our combined weight would put us outside the CG envelope,...he had no idea!

 

I would bet this happens more often (especially at flight schools) than flying while exceeding max gross weight?

[ridethisbike]

In your first post.. you meant to put "as you BURN fuel, your situation will not improve," right?

[pilot#476398]

In your first post.. you meant to put "as you BURN fuel, your situation will not improve," right?

No, in a Robbie improving your CG with fuel burn only works when its too far aft.

 

Start with a zero fuel weight & balance. With 400lbs in the cockpit the CG will be too far forward. Since the CG envelope slopes backwards (shrinks), look at the graph, when you add fuel your CG keeps its position relative to the forward line! Thus remaining too far forward.

 

Technically you are correct though. As you burn off fuel your situation will not improve with forward CG.

[ridethisbike]

Technically you are correct though. As you burn off fuel your situation will not improve with forward CG.

 

I thought this is what you were getting at, which is why i said what I did. After this explanation and rereading the first post I now realize that you meant if you were at zero fuel and forward of that 1275-1370 line, then yes, absolutely adding fuel will not help your situation at all! Simple misunderstanding.

[Plumberpilot]

Looks like the R22 should have a little weight you could hang somewhere out on the tail boom to correct for a heavy crew weight like a Hiller.

[Wally]

How many of you check the CG at all?,...especially you tour guys?

 

EMS in an Astar- I calculate the maximum patient weight for the stretcher every day, every crew change, and have a spreadsheet on my phone to recalculate with changes made if I have a heavy patient. Not terribly enthusiastic at suddenly being a test pilot (out of cg) when my next emergency occurs. Call me lazy...

[Nearly Retired]

Correction: Under part-135 you won't *always* have a load manifest. Under part-135 you don't even have to calculate your GW and CG on every flight; only the pilots of twin-engine aircraft have to do that. In all my single-engine 135 flying, I hardly ever got a load manifest. (Then again, I haven't flown 135 since "9/11" so maybe things have changed even though I couldn't find anything specific that addressed the subject in the FARs.)

 

PHI used to give us 206 drivers little rule-of-thumb guidelines like, "You must have one pound in the copilot seat for every pound in the baggage compartment." And of course the 206L has diagrams on where to seat the people to generally stay within CG.

 

With most helicopters it's not hard to dream up a little spreadsheet in which you can plug in the variables and see what the GW and CG are. Using such a device, you can quickly and easily come up with different scenarios. Again at PHI, I did a couple of "most aft CG" and "most forward CG," printed them off and kept them on my manifest clipboard. Anything in between and I was golden. Fuel burn doesn't appreciably affect the CG in a 206B so much, although it does in a 206L and you have to account for that.

 

I found out, for example, that in the particular 206 I was flying, I could carry 80 pounds in the boot with nothing else in the cabin but me, even at most-aft fuel CG. Comes in handy when they say, "Take this anvil over to Foxtrot platform," and you don't want it in the back seat.

 

I also found that the weight restriction on the front (copilot) seat was so high that a guy would physically not be able to fit before his actual weight was a problem. "Hop in the back, slim! The seatbelts are longer back there."

 

So you run through the various scenarios and then you don't have to calculate a GW/CG for every flight. Even the tour guys can (and I'm sure do) do this.

 

The bottom line is that whatever your particular loading is, you lift off the ground slowly and carefully and deliberately EVERY TIME. Then you see how the thing is "hanging" in the hover. Chances are it'll be fine. But if you have the stick back in your gut, or you're straight-arming the bitch, that should clue you in that something's not quite right.

[Spike]

Depending on equipment and/or pax changes, I’ll recalculate W&B every flight. I also have a worst case scenario and zero fuel comparison along with a weight tabulation spreadsheet on my kneeboard….

 

All of our gear is pre-weighed and marked with that weight. Crewmembers are weighed with all of their gear on. Estimations are now the exception, not the norm….

 

In the past, I would just do a worst case scenario and the used weight tabulation chart for changes. However, with the advent of SMS and accreditation standards, I prefer not to just “talk-the-talk”…. In fact, prior to every launch, I complete and document (hard copy); weather, W&B, notams, TFR’s, pax manifest and a risk assessment. The results are combined into 3 packages. One is posted on a “preflight action” clipboard hanging on the wall in our main office. The second is carried with me. The third is locked up and only accessible to family members in case of death or incapacitation….

Edited May 7, 2013 by Spike

[pilot#476398]

^{The bottom line is that whatever your particular loading is, you lift off the ground slowly and carefully and deliberately EVERY TIME. Then you see how the thing is "hanging" in the hover. Chances are it'll be fine. But if you have the stick back in your gut, or you're straight-arming the bitch, that should clue you in that something's not quite right.}

 

^{This is kinda where it all started for me. A couple of times I've gotten with a CFI I haven't flown with before. I ask him for the numbers so I can do a W&B and he says, I already took care of it. I figure, he's a CFI, so I can trust him,...right?}

 

^{The flight goes just fine, and the R22 flies just as it always does. For next time though, I find out how much he weighs and do my own W&B,...only to find out that we're over the forward line!}

 

^{The chopper flew just fine (which perhaps is why these CFIs seem ok with flying it out of CG), but is there any unseen damage that's being done?}

[Spike]

^{The chopper flew just fine (which perhaps is why these CFIs seem ok with flying it out of CG), but is there any unseen damage that's being done?}

 

This is a typical entry level check-ride question…

 

"What’s the problem with flying a helicopter that’s out of CG?"

 

Answer this and you'll understand it's not about "unseen damage"....

Edited May 7, 2013 by Spike

[adam32]

Looks like the R22 should have a little weight you could hang somewhere out on the tail boom to correct for a heavy crew weight like a Hiller.

 

Well we all know that ol Frankie isn't nearly as smart as ol Stanley

[pilot#476398]

 

This is a typical entry level check-ride question…

 

"What’s the problem with flying a helicopter that’s out of CG?"

 

Answer this and you'll understand it's not about "unseen damage"....

 

The answer I gave on my checkride was that if its too far forward you could run out of aft cyclic before you can slow down (i.e. if you're going 80, you may only be able to slow it down to 60, then you have to try and land at 60kts!). The other part was not being able to flare in the event of an auto.

 

...but that doesn't answer my question, since the helicopter still flew just fine out of CG, even when we were just about out of gas!

 

So, again I ask; Is there something else?

[Hobie]

These things have a huge amount of engineering testing and analysis attached to the operating manuals for us to second guess them.

[Wally]

 

The answer I gave on my checkride was that if its too far forward you could run out of aft cyclic before you can slow down (i.e. if you're going 80, you may only be able to slow it down to 60, then you have to try and land at 60kts!). The other part was not being able to flare in the event of an auto.

 

...but that doesn't answer my question, since the helicopter still flew just fine out of CG, even when we were just about out of gas!

 

So, again I ask; Is there something else?

 

Did you have any sudden power losses at cruise speed, power set and all trimmed up? Sometimes when that happens, the pig yaws, rolls, pitches down. You really really really and truly want to get that nose up before your NR is unrecoverable, which is related to how much aft cyclic and the rate it can bring the nose up. I don't know that that's the answer, but "helicopter pilots know that if something bad hasn't already happened, it's about to..." (Harry Reasoner)

[Spike]

 

The answer I gave on my checkride was that if its too far forward you could run out of aft cyclic before you can slow down (i.e. if you're going 80, you may only be able to slow it down to 60, then you have to try and land at 60kts!). The other part was not being able to flare in the event of an auto.

 

...but that doesn't answer my question, since the helicopter still flew just fine out of CG, even when we were just about out of gas!

 

So, again I ask; Is there something else?

 

IMO, your answer is incomplete……

 

It will fly just fine until you need to apply maximum cyclic control inputs. Maximum control inputs are required during excessive maneuvering. Excessive maneuvering is mostly associated with emergencies. If you’ve never made a cyclic control input larger than a quarter, then you’ve never experienced excessive maneuvering (low-g recovery comes to mind along with turbulence or a real engine failure and even SWP).

 

With that, fat, dumb and happy never believe anything bad will happen so they just keep going….

 

Any CFI (or pilot in general) who ignores the CG envelope is asking for trouble. EVERY accident report reads, “Everything was functioning okay UNTIL........”. That UNTIL could happen on your next flight. Therefore, on your next flight, are you going to sit down and do some simple math and plot a couple dots on a chart or, are you going to trust some fat, dumb and happy CFI….. Again…….

 

Learn what is necessary to stack the chips in your favor…..

 

Edited May 7, 2013 by Spike

[pilot#476398]

I was just wondering if there might be any danger of structural damage, from repeatedly flying out of CG?

 

This flying outside your limits, pulling too much power, etc... its all up there with fudging the logbook,...and I suppose, human nature!

Edited May 8, 2013 by pilot#476398

[JDHelicopterPilot]

As a student I was required by the school and CFI to calculate my weight and balance each and every flight. The balance portion referes to CG. Also, on a check ride the examiner is going to want to see it as well, as a requirement for the PTS.

 

As a CFI I required as did my flight school that all students calculate actual weight and balance for each flight.

 

Take that a step farther, I also required my students to do performance planning as well. What is my HOGE and HIGE?

 

Both of these tasks are basic flight planning items which should be done prior to each flight.

 

A recent AS350 crashed with 4 fatalities as a result of improper or rather no flight planning/preflight.

 

I truly hope each pilot knows the weight and CG of their aircraft on the flight they are on. It is not that hard. It is even easier these days with all the apps you can get for the tablets and smart phones.

[Astro]

 

The answer I gave on my checkride was that if its too far forward you could run out of aft cyclic before you can slow down (i.e. if you're going 80, you may only be able to slow it down to 60, then you have to try and land at 60kts!). The other part was not being able to flare in the event of an auto.

 

...but that doesn't answer my question, since the helicopter still flew just fine out of CG, even when we were just about out of gas!

 

So, again I ask; Is there something else?

 

Robinson Safety Notice 37 talks about exceeding limits and metal fatigue. It mentions exceeding MAP and gross weight, so I would imagine that exceeding CG limits would count too?

[Renaud]

Sorry guys, but on this subject I need to express my opinion about CG and GW (both topics)

 

As far as remember during my post maintenance technical course (FW):

 

1. CG is related to flight behaviors.

2. GW is related to structural design.

 

° During design, conception and test flights, manufacturers determine CG limits to guaranty a certain capacity of maneuverabilities for the aircraft.

This capacities are established to permit to fly and to covers "any" emergencies within a flight envelop.

 

Going out of GC is jeopardizing this capacities and the designed flight envelop, means the purpose of the aircraft. (notwithstanding with the regs)

 

° GW is established to guaranty a strength against turbulences, load factors, age, etc...

 

Example: An aircraft is designed to have a MGW of 1000 lbs.

Manufacturer certify that his ship could sustain at 1000 lbs a total aerodynamic load of 3 G's, could resist a gust of 50ft/' and stand for let say 20 years.

 

If you constantly bust limits, the integrity of the hull, therefore all aircraft and mechanism's assemblies are not anymore within design limits.

 

In our example, after 5-10 years, the hull broke in flight.... design fatigue exceeded!

Most of the time the aircraft will not broke with you, but with the other one behind you.

Or you might be the other behind a fellow who busting limits all the time... who knows!?

 

Except doing a Non Destructive Test every time, nobody is able to know how the metal memorize any abuse and when it will said "no more".

 

Even if for the purpose of certification, test pilots, manufacturer wrote limits with a safety factor, we are not allowed (and certainly not able) to tell how much is the factor and calculate "our" new limits!

 

So, we as aviators put our trust and confidence on manufacturers, mechanics, other fellow aviators to respect these limits for the benefit of all.

 

As technical pilots, our duty is to check if the A/C match what the manufacturer said is the minimum performances for the certificated type.

 

On Daily basis, you as pilot in command (behind controls and/or pilot in charge of the flight) your duty is to be sure you use your ship within limits.

 

Knowingly accepting to "push" limits is IMHO a complete lack of airmanship and bound to be grounded Ad vitam æternam.

 

 

I actually flew an A/C build in 1979 with 41 300 hrs and 84 000+ cycles!

Let me tell you that each time we go trough turbulences, we slow down well below VA... even if this A/C has been well maintained and overhauled more than ones.

 

We are not in a hurry for 1 or 2 minutes.

So please gentlemen, future old timers, experienced pilots, young pilots, students, etc... stick to limits.

 

As student, you could always take 1 or 2 gallons less fuel for your flights.

 

For those who work with "numbers":

On the R22, 2 gallons of fuel represent around 14' running time, 12 lbs, >1% of total GW, 1/8 inch on MAP, 240ft on HIGE!

[Gomer Pylot]

It really depends on the aircraft, as to whether I check CG. I don't check it on the model I currently fly, because I know it's not possible to exceed any CG limits while within MGW limits, or even while well over gross. But on other models it can be easy to get out of limits, and then you need to do at least some quick checks. Part 135 allows the use of sample loading tables for single-engine aircraft, and with experience you should know very close to where the CG will be before lifting off If there is any doubt, check.. CG limits are definitely a controllability issue, not a structural issue, at least until lack of control causes structural problems. Then you have real problems.

[JDHelicopterPilot]

To the point,

 

Flying the aircraft beyond the limitation of the RFM is unprofessional and unethical. As of late I am seeing a number of accidents that can be attributed to this kind of behavior and it has me a little frustrated. Remember, "Protect the sacred trust." (Mike Franz)

 

Your crew, passengers and quite honestly your family are trusting you with their lives. As a pilot we have a duty to protect that.

 

As of late there have been a number of fatal accidents in the last 3 years as a result of pilots saying "watch this" and lack of proper basic preflight actions. As a result innocent passengers and crew have paid the price.

 

We have to get back to the basics. Proper flight planning, preflight and no showing off.

 

If I want to go out and screw around, I will do it on my own in my own helicopter. We as professional pilots need to protect that sacred trust.

[Nearly Retired]

I was talking with one of the pilots who did the initial flight test certification of the FH1100 helicopter - way back when. He said that one of the things the FAA demanded was that they ballast the helicopter to its fully aft/left CG, then take it up to the service ceiling and make FULL control inputs. Stop to stop. Think about that. I was literally aghast. I made some stammering, dumb comment about how, um, "exciting" that must have been. The test pilot was not so diplomatic. I cannot repeat his answer in this family-friendly forum, but let's just say he was colorfully succinct and unabashed about how scary it was.

 

He also told me about some of the other test procedures they had to accomplish. It all made me damn glad I was never a Production Test pilot. Damn glad.

 

Being overgross or out of CG by "a little" probably won't kill you...at sea level...on a cool, calm day...when you're at your personal 100%. But that's not the point, is it? Are you the type who goes by the book or not? Do you adhere to rules and regulations or not? As JD notes, aviation is all about trust. Lots of people trust us to fly these things "right." And like I said, I don't want to be a test pilot.