Tag Archives: flight training

So You Want to Be a Helicopter Pilot, Part 6: Study Hard

Posted on by
12

Flying a helicopter is more than just knowing how to move the controls and perform maneuvers in flight.

As with any other skill you might acquire in life, learning to fly helicopters is made up of many components. The most obvious is getting the motor skills — including reflex reactions — to handle the actual mechanics of flying: working the controls, etc. But behind all that is the knowledge you need to acquire so you fully understand what to do, why you need to do it, and how it works.

Ground School

Ground school — time spend on the ground with a flight instructor learning the what, why, and how parts of flying — is an important part of flight training. Unfortunately, it’s not usually the fun part and, because of that, most pilots try to minimize it. Instead of learning as much as they can about ground school topics such as aerodynamics, aircraft systems, weather, and physical (or medical) issues, some pilots learn only as much as they need to know to pass the written and oral tests that come later.

This is not a good idea if you intend to build a career as a helicopter pilot. At some point in your career, the gaps in your knowledge will be noticed — perhaps by the chief flight instructor you hope will give you your first job or by the chief pilot who can put you in the seat of a turbine helicopter. Or maybe by the mechanic who asks you to perform and document power checks in flight and you clearly don’t understand what he’s talking about. Or maybe by the new pilot you’re asked to show around — the pilot who did study hard and realizes how clueless you are.

Ground school is where you can learn what you need to know, with an experienced flight instructor who’s there to answer your questions. Dig in and learn. Make sure you understand everything — if you’re hazy on something, ask questions. Discuss topics with other student pilots and flight instructors. When you fly, try to understand how ground school topics apply to flight. Take notes, review them, jot down things in the margins when you connect the dots between topics later in your studies or during flights.

Hitting the Books

There are many books and study materials that can help you understand and learn the topics you need to know.

I’ve already pushed the excellent FAA publication, Rotorcraft Flying Handbook, several times on this blog, but I can’t recommend it often enough. Where else are you going to find a free, generously illustrated guide that explains much of what you need to know about flying helicopters in terms anyone can understand? It’s an excellent starting point for your studies.

FAR on iPadAnother pair of must-have publications is the Federal Aviation Regulations (FARs) and Auronautics Information Manual (AIM) which are often published in the same volume. The FAR is updated throughout the year and most publishers publish new editions annually. You should get the most recent edition when you begin your training and try to update it at least every two years. Or do what I do: buy it in app format for an iPad (shown here) or iPhone. You can find them both on Tekkinnovations.com; once you buy them, updates are free (at least they have been so far for me).

Another handy book to have in your possession is a copy of the Pilot Operating Handbook (POH) for the aircraft you’ll be flying during most of your flight training. Yes, I know there’s one in the helicopter — it’s required to be there — but unless you plan to sit in a helicopter to do you studying, it’s nice to have your own copy to jot down notes, etc. I learned to fly in an R22 and bought a copy of the POH the first time I attended the Robinson Factory Safety Course; I added all kinds of notes in the margins during that course.

Cyclic & CollectiveThere are other books about flying helicopters. Many of them have been written by experienced helicopter pilots. One of my favorites is Cyclic & Collective by Shawn Coyle. This is a huge book jam-packed with information that goes beyond the basics offered by the FAA.

It’s likely that your flight school will also recommend or require certain books to help you study. The Jeppesen books are a big hit — especially to your wallet. But, to be fair, they do have excellent illustrations to make important points clear.

But remember, buying a book isn’t enough. You have to crack it open and read it.

Going the Video Route

There are also training videos that you might find helpful to reinforce what you learn in ground school and on your own. I used the King School videos. Although the series is designed for airplane pilots, there was an extra video in the set that covered helicopter operations. In general, I found the videos painfully boring at times, but I admit they were informative. By the end, however, I wanted to grab John and Martha King and crack their heads together. This, of course, was more than 10 years ago; hopefully, the videos have been revised by then. There’s also a good chance you can some of this material on their website.

I think Sporty’s has a set of videos that compete with the King’s — so you might want to check that out as an alternative.

If you decide to buy the videos, I bet you can find them used on eBay or Craig’s List for less than regular price. You can always sell them when you’re done.

Make It Count

Your flight training will cost as much as — if not more than — a college education. You need to take it just as seriously.

If you fail to learn the concepts by studying hard and asking your flight instructor to explain things you’re struggling with, you’re not only throwing away the money you’re spending on your education, but you’re setting yourself up for failure in your career.

Make it count by putting real effort into it and studying hard.

Next up, I’ll explain why you shouldn’t hit the books with a bag of chips within reach.

Helicopter Academy / Boatpix

Posted on by
17

What do YOU think?

Despite the fact that my contact page clearly says I do not give career advice, I got the following e-mail message today:

I have read some of your posts and would love to hear your opinion. I am working on my helicopter commercial license and I came across helicopter academy. They offer low hourly rates and train you to work hand and hand with boatpix.com They guarantee to get you to 300 hours and guarantee you a CFI job and aerial photographer. The contract does not actually state they will gurantee hire you after your training. They give you their “word” As a fellow aviator I know people tend to make things up just so you pay for the flight as they sit back and build their own time. Do you know of this flight school? Is it the real deal? I would appreiciate your thoughts on the matter. Thanks for your time.

What do I think? I think that a promise from a flight school — or any other organization interested in getting you to sign on the dotted line — is as good as the paper it’s written on.

Reacting to Low Rotor RPM

Posted on by
6

Yeah, I know RPM = life, but think about it, guys!

I did my monthly perusal of the NTSB helicopter accident reports this morning and this one jumped out at me. It’s another instance of a pilot reacting badly to a low rotor RPM situation. (You can read my favorite example of a poor response to low rotor RPM here.)

The report is short and, for some reason, cut off before the end. (NTSB seems to be having trouble with its database lately.) Here’s the story:

The commercial helicopter pilot reported that he was on a Title 14, CFR Part 91 business flight transporting one passenger and seven dogs to a remote camp. He said as he approached the camp, which was at 3,800 feet msl on a snow-covered glacier, flat light conditions made it difficult to discern topographical features on the glacier, so he elected to land at an alternate landing site at 3,200 feet msl to wait for conditions to improve. During the approach to the alternate site, just before touchdown, the pilot said the low rotor annunciator horn sounded, and he lowered the collective to regain rotor rpm. The pilot said he was unable to initiate a go-around, so he brought the helicopter to a hover, but due to the prevailing flat light he was unable to discern his height above the site, and he unintentionally allowed the helicopter’s left skid to touchdown on the uneven, snow-covered terrain. He said that there was an “instantaneous dynamic rollover” as the helicopter rolled to the left, the main rotor blades struck the snow, and the helicopter came to rest inverted. The helicopter sustained substantial damage to the fuselage, tail boom and main rotor drive system.

Glacier Crash with Dogs

Coast Guard photo of crash site. We’re taught to keep the shiny side up. Note dogs.

The two human occupants were not injured. They don’t say anything about the dogs, but since they were likely crammed into the back seat area, they probably cushioned each other and are okay, too. (Seriously, who puts seven dogs in the back seat area of a 4-seat helicopter?)

About Low Rotor RPM

Helicopter pilots have a saying: RPM = life. It means that if your blades are spinning fast enough, you should be able to fly. But if you lose RPM, there’s a chance that you might drop out of the sky (yes, like a brick) and have a very ugly encounter with the ground. Why? Because the spinning of the rotor blades is what gives a helicopter lift. If they stop spinning, they’re not generating lift. If they’re not spinning fast enough, they’re not generating enough lift to keep the helicopter airborne.

Helicopters have low rotor RPM warning systems. In an R44, it consists of a light on the instrument panel and a “horn.” The sound of the horn is very annoying and impossible to miss. (See for yourself here.) Because RPM is so important, the full system — light and horn — are required for flight.

On a Robinson helicopter, the low rotor RPM warning system kicks in at 97% RPM. Since the helicopter is operating at 102% RPM, that’s just 5 units below normal operation. But as they teach in the Robinson Safety Course, the helicopter should be able to fly with RPM of 80% + 1% per 1,000 feet of density altitude. Using this accident altitude as an example and assuming that it wasn’t above the standard day temperature of 15°C at the “snow-covered glacier” landing zone, the helicopter should have been capable of flight with rotor RPM as low as 84% or 85% (see density altitude chart). I use the word should (and italicize it for emphasis) because this is a rule of thumb. I do not recommend flying a helicopter below normal operating RPM. This rule of thumb just helps pilots understand how critical a low rotor RPM situation might be.

What causes low rotor RPM? Engine malfunction is one cause. A bad magneto or stuck value could rob the engine of horsepower, thus preventing it from keeping the rotor RPM where it needs to be. Performance needs beyond what the engine can produce is another. For example, it takes more power to hover than to fly; attempting to hover with a heavy load at high density altitude could result in a loss of rotor RPM. That may have been the situation here; the pilot was in an R44 Raven I (or possibly an Astro) at more than 3,000 feet density altitude at or near max gross weight*.

Emergency!

During flight training, helicopter pilots are trained to react to low-rotor RPM situations. In fact, Robinson helicopter pilots get extra training every two years (per SFAR 73) because of the unusually high number of low RPM accidents in early Robinson helicopters. Although modern-day Robinsons have correlators and governors to help the pilot maintain proper RPM, this special training and endorsement is still required.

Low rotor RPM is treated as an “emergency.” That means it has an emergency procedure associated with it. Helicopter pilots are drilled on the procedure until it becomes second nature.

Page 3-10 (in the “Emergency Procedures” section of the R44 Raven II Pilot’s Operating Handbook) states:

A horn and an illuminated caution light indicate that rotor RPM may be below safe limits. To restore RPM, immediately roll throttle on, lower collective and, in forward flight, apply aft cyclic.

As a result, when we hear that low rotor RPM warning horn — which is directly related to the deterioration of life-giving RPM — we react quickly to recover lost RPM. That means increasing throttle (to add engine power) and lowering the collective (to reduce drag caused by the rotor blades). Pulling back on the cyclic, when moving forward, can also help recover lost RPM by transferring energy in the forward speed to rotor RPM (which is why RPM increases during a cyclic flare in an autorotation).

Lots of folks argue about which is more important and whether you need to do all three. I think rolling on the throttle is most important but will acknowledge that it doesn’t always resolve the problem. Lowering the collective usually helps.

Hold that Collective

While that is all well and good, I’d like to make this radical suggestion: is lowering the collective to recover RPM a good idea when you’re within 10 feet of the ground?

In this accident, the pilot heard the low rotor RPM horn “just before touchdown.” I’ll be generous and take that to mean anywhere within 10 feet of the ground. So he’s coming in for a landing. He’s already got his descent going and he’s either increasing power to bring it into a hover or he’s past that point and is reducing power gently to touch down. Either way, lowering the collective will cause him to descend faster than he already is. (It doesn’t say anything about rolling on the throttle; did he?) He’s less than 10 feet from the ground. The report goes on to state that he was able to bring it into a hover but was apparently lower than he thought (perhaps because of his collective work?) and touched a skid to the snow, causing dynamic rollover.

Low Rotor RPM Might Not Always be an Emergency

I’d like to argue that low rotor RPM is not an emergency situation when you’re very close to the ground.

After all, what’s the worst that can happen? At less than 10 feet, you don’t need the RPM to keep you alive. Even if the RPM dropped to 0 when you were only a few feet off the ground, you’re not going to die. You’ll drop like a brick — a few feet. Spread the skids a little. I don’t even think the belly would touch the ground. If it did, the seats would collapse as designed and (literally) save your ass. We’re talking less than 10 feet here.

Instead of dealing with low rotor RPM when you’re less than 10 feet from the ground, doesn’t it make sense to ignore the horn and just land?

Remember, in an R22 or R44, the horn sounds at 97% RPM. In this example, he could still remain in flight with the RPM all the way down to 85%.

Let’s review. The pilot is at a critical moment of flight: landing, just before touchdown. The low rotor horn goes off, zapping his concentration. Instead of completing the maneuver he was almost done with, a maneuver that would put him safely on the ground, he switches gears to handle the sudden “emergency.” That reaction just puts him closer to the ground with him focused more on the RPM situation than the ground he could very well make contact with. As a result, he botches the landing, possibly distracted by a non-emergency “emergency.”

A side note here: I have witnessed a low-time pilot literally freezing up when the low rotor RPM horn sounded on landing. I was sitting beside him, horn blaring, in a hover 3 feet off the ground at a very high density altitude airport — 10,000 feet. His brain simply shut off. I repeated the words, “Just set it down,” three times before he snapped out of it. There was no danger, but the damn horn sent him into some kind of mental seizure. If that happens in cruise flight, he’s definitely dead.

The horn is scary. We’re trained to react to it. But is low rotor RPM recovery always the answer? I’ll argue that any time you’re very close to the ground, you need to think about the consequences of all of your actions before making them. Don’t react to an emergency that doesn’t exist.

—
* Doing the math… I don’t have the details of the accident flight’s weight. But if you figure two grown men weighing at least 180 pounds each and seven 50-pound sled dogs in the back, you have 710 pounds for just the cabin occupants. A Raven I with minimal equipment weighs at least 1440 pounds. So that brings a total of 2150 pounds. Add half tanks of fuel for another 150 pounds; that’s a total of 2300 pounds. The max gross weight of a Raven I is only 2400 pounds. So with my guesstimates, he was pretty close to max gross weight.

Now because I know the mentality of the helicopter forum participants who often lurk here (and then share their opinions about me in the forums they troll), I feel compelled to defend my calculations here instead of in the comments thread. (I don’t waste my time in the forums anymore.)

The dogs were “sled dogs,” which you’d expect since that’s the kind of dog most useful at “remote camps” in Alaska. They were later rescued by the Coast Guard, which airlifted them off Godwin Glacier after the crash. I’m estimating 50 pounds each, but they could easily be larger. Here’s a photo of them. (Frankly, I’m having trouble imagining seven 50-pound dogs crammed into the back seat area of a helicopter like mine. I’m also cringing at the thought of vacuuming all the shedded fur out.)

And yes, both the pilot and the passenger could have been Weight Watchers graduates weighing in at 140 pounds or less each. And they could have been wearing shorts and sandals. Or nothing at all. And there might have been only 10 gallons of fuel on board.

But my guesstimates are based on what I’ve experienced in reality. People are fat and like to bring unclaimed baggage, pilots like to take as much fuel as they can for missions in remote areas. It’s far more likely that the passenger was even bigger and had gear with him and the pilot had his tanks much closer to full than empty. But until the FAA releases more info — which is not likely, since there was no fatality in this accident — guesstimates are the best we can do.

Helicopters 101: Flight Planning

Posted on by
1

The basics of cross-country flight planning for helicopters.

Articles in the Helicopters 101 series:
– Flight Planning
– CG
– Weight
– Hover Charts
– Ground School

Recently a reader of this blog wrote to suggest that I cover cross-country planning as a blog topic. I searched my archives and found that I already had. My post, “Flight Planning,” goes into a great deal of detail about the process I use to prepare for Part 135 charter flights, which require a complete flight plan. But that’s probably not what this reader was talking about. I think he was more interested in the nuts and bolts of creating a flight plan.

This weekend, I have to make three relatively long cross-country flights:

  • Wickenburg, AZ (E25) to Page, AZ (PGA) – 189 nm direct
  • Page, AZ (PGA) to Salt Lake City, UT (SLC) – 232 nm direct
  • Salt Lake City, UT (SLC) to Seattle, WA (BFI) – 601 nm direct

I’ve flown the route from Wickenburg to Page and back numerous times. I’ve done Salt Lake CIty to Page once and Seattle to Salt Lake City once. I figured I’d use the PGA to SLC flight, which I’ll be doing alone, as an example of how I plan a flight.

Weather

A few days before the scheduled flight, I start checking the weather along my route. I use the National Weather Service’s NOAA Web site for weather information. After all, the NWS is the source of all the weather data for the United States. That’s where the Weather channel and Duats and the FAA get raw weather data. Although each weather reporting organization may interpret it slightly differently, it’s all based on the same stuff. And the NWS site doesn’t bombard me with obnoxious advertising.

A lot of folks use the Aviation Weather link to get aviation weather information. I don’t — at least not a few days out. Remember, I’m flying a helicopter. I’m 500 – 1000 feet off the ground. I don’t care much about upper level disturbances, the jet stream,or icing in clouds. I’m not getting anywhere near that stuff.

Page Weather

The graphic weather forecast for Page on the morning this post was written.

What I’m interested in is forecasted conditions for the departure and arrival airports, as well as any cities in between. So, in this case, I would check out the weather forecast for Page, Salt Lake City, and possibly Richfield, which is roughly halfway between the two. I’ll pay close attention to the forecast for my day of travel, as well as the day before and after.

What I see today is relatively poor forecasted conditions for Saturday, the day of my flight, with chance of rain or snow at each location. Not what I want to see, but remember, it’s a forecast. It will probably change. I have to hope it gets better.

Route

Next, I plan out my route. Although I listed straight-line distances at the beginning of this piece, I seldom fly in a straight line. Instead, I try to find a route that’s a compromise between a straight line — which, out in the desert, usually means doing a lot of flying in the middle of nowhere — and following roads — which is where people will be if I need help.

Now I need to make it clear that unless there’s a road going the way I need to go, I’m not going to follow roads to get from Point A to Point B. I don’t want to go out of my way — at least not too far. Helicopters are expensive to fly and I’m not made of money. The time budget for this trip is 2 hours — that’s what the client paid for — and I’ll need all of it and then some. So what I want is a compromise that puts me near roads for part of my trip.

I plan my route with charts. World Aeronautical Charts (WACs) are very handy for long cross-country flight planning. But sectionals offer more detail.

Of course, I cheat. I use SkyVector.com. It puts the charts onscreen and enables me to do some very basic flight planning — mostly distances and directions. As the site warns — probably with the advice of lawyers — it’s not for navigation or preflight use. But I use it for preliminary planning. It really helps me get a good idea of where I need to go.

Options

The pink line at the bottom is the direct route from Page to Brice; the red and blue lines are my two options for continuing northbound without overflying 10,000 foot mountains.

In this case, I’m seeing that a direct flight from Page (PGA) to Bryce Canyon (BCE) would take me 57 nm mostly over remote, high desert terrain, climbing from about 4300 feet to over 7000 feet. No major mountain ranges to cross along the way — and that’s good.

From there, I can follow the East Fork of the Sever River and the road beside it northbound between a pair of mountain ranges topping out at over 10,000 and 11,000 feet, then follow a pass that’ll hook me up with Highway 89. This map shows it as the red route. That’s the way I flew last time and the only drawback I recall was the rough air in that pass.

The other option is to continue on almost the same heading to Panguitch (U55), which will hook me up with Highway 89. I can then follow that northbound between two mountain ranges topping out at 11000 feet, staying slightly lower in overall altitude and sticking with a well-traveled road. This map shows it as the blue route.

Completed Route

My planned route, roughed out on SkyVector.

I continue this process for the entire trip. This one’s pretty easy; I’ll be following Route 89 most of the way. When I get to the outskirts of Salt Lake City, I’ll be following I-15. This turns my 232 nm trip into a 259 nm trip and adds at least 15 minutes of flight time. But I’ve minimized my flying time over the middle of nowhere without detouring too much out of my way. The WAC charts I pasted together here from SkyVector screenshots give you an idea of what the entire route looks like. I can also see that my flight without wind could be as long as 2-1/2 hours. My helicopter’s endurance is just 3 hours, so I need to consider the possibility of needing a fuel stop if I hit headwinds. Fortunately, there are plenty of airports with fuel along the last 50 miles of my route.

By the way, the main benefit to following a road when you enter busy airspace and don’t know the local reporting points is that you can state your position to ATC in relation to the road. For example, “Helicopter Zero-Mike-Lima is ten miles south over I-15” is a very definite location.

Once I get a rough outline of the course, I go into detail with sectional charts. I buy them as needed for my cross-country flights. I’ll check to be sure there’s no special airspace or weird activity (think gliders and ultralights) along the way. I’ll also look for charted power lines — not that I’ll remember them when the flight time comes. I’ll make a cheat sheet of airport names, designators, elevations, and frequencies so they’re easy to enter into my GPS for added navigation assistance during flight.

Although I don’t usually mark up my local charts (Phoenix sectional and terminal area chart), I don’t mind taking a highlighter to the Las Vegas and Salt Lake City Sectionals I’ll use for this trip. I’ll also have a Salt Lake City terminal area chart on hand. Before I start my flight, I’ll fold them all neatly to expose the route. With just one hand to fiddle with charts, it’s much easier to prepare before lift off.

Destination Information

On this particular trip, I’ll be landing at Salt Lake City Airport, a Class Bravo airport I’ve never landed at before. I’ll need to know where on the airport I’ll be landing so I don’t sound like a complete idiot when I talk to the tower.

Airport Diagram

The airport diagram for SLC. General aviation is handled in the southeast corner, not far from the I-15 freeway.

I could pull out my Airport/Facilities Directory and look up the airport, but that green book is already stowed in the helicopter for the trip. So instead, I’ll hop online to the FAA’s AeroNav Services (formerly NACO) web site. Once there, I’ll click the link for Free Digital Products and then click d -TPP and Airport Diagrams on the page that appears. (Note that you can get a PDF of the page(s) for a specific airport from this site, too.) I’ll use links and search to get the Airport Diagram for SLC, which will be downloaded as a PDF. I can print it out for future reference and put it with my charts.

I’ll also go to AOPA Airports and get information for SLC. I’m interested mainly in FBOs. I was told to go to Million Air, so I want its location, frequency, and phone numbers. AOPA Aiports also shows a zoomed in satellite image of the FBO’s location, making it easy to mark on the airport diagram.

While I’m at the AOPA Airports site, I’ll also jot down the phone numbers for the AWOS or ASOS systems along my route. I’ll program these into my cell phone. This way, if I need up-to-date weather information for a specific airport, I can get it by simply calling. This has come in handy in the past in marginal weather conditions. I have quite a few airports stored in my computer and phone.

Note that I always get airport frequency information from FAA sources: up-to-date charts or the Airport/Facilities Directory. No online database that isn’t maintained by the FAA is guaranteed to be accurate. There’s nothing worse than trying to land at a towered airport and having the wrong frequency for it. I’ll also update my Garmin 420‘s database before this flight. I have an annual subscription, but I often skip updates because they’re such a pain in the butt to install.

Final Planning

I’ll keep watching the weather all week. If it starts to look like its getting worse, I’ll start thinking about rescheduling my trip. In all honesty, the only thing that would stop me from doing the flight would be winds in excess of 40 miles an hour (possible, but not likely), low clouds (definitely possible), or freezing rain (possible). Although I mostly fly in great weather here in the desert, I’ve flown in ugly weather, too. A fair weather pilot should not be flying for hire.

The day before the flight, I’ll call Million Air and tell them to expect me. I don’t have to do that, but it’s better than just dropping in. They’ll also give me some insight about where to land/park. I’ll note it on my airport diagram.

The day of the flight, I’ll check the weather again. This time, I’ll use Duats.com. I’ll punch in my flight plan airports and let Duats tell me the official aviation weather and notams and give me a more precise (official) flight plan that factors in the wind.

Could I do it by hand? Yes, if I had to. But I don’t so I don’t.

I’ll also make my fly/no fly decision.

I’ll file a flight plan via Duats. I might forget to open it when I take off, though. I often do when I fly by myself. But I have a Spot Messenger that broadcasts my location to a Web site that my husband monitors. I think that’s better flight following than I could get from the FAA without climbing to 12,000 feet. (Keep in mind that I don’t have oxygen and the R44 vibrates like a coin op motel bed at altitudes above 9500 feet.)

That’s About It

That’s all there is to it. The longer the flight, the more variables to consider. This is a pretty short one. The flight from Salt Lake City to Seattle is another story. Lots of variables there. My co-pilot on that trip will plan and fly the entire route. I’ve already looked at the route he suggested and it seems fine to me. I’ll just follow along on the chart.

The main thing that makes this different from planning for an airplane flight is the altitude issue. Airplanes climb several thousand feet over terrain. Mountains don’t get in their way; they’re above the mountains. Helicopters generally don’t fly that high, so we often look for routes that take us around obstacles like 11,000 foot mountain ranges. We also have the luxury of being able to land almost anywhere if we have a problem

Helicopters 101: CG

Posted on by
1

The other half of the weight equation.

Articles in the Helicopters 101 series:
– Flight Planning
– CG
– Weight
– Hover Charts
– Ground School

Last week, I wrote a blog post about helicopter weight. It was my response to a blog post by Tim McAdams on the AOPA helicopter blog titled “Gross weight.” The comments to that post indicated to me that some of the commenters were confusing weight with CG — center of gravity — issues. My blog post concentrated on weight, putting CG aside. But CG is the other part of the weight equation. And for most helicopters, CG is vitally important to calculate as part of preflight planning.

CG Defined

Center of gravity is pretty much what the phase indicates: a calculation of the center of gravity on an aircraft. It’s the aircraft’s balance and it’s calculated as part of the “weights and balance” computations.

For helicopters, CG is extremely easy to envision. After all, a helicopter with a single main rotor system (as most have) is supported at one point in flight: the main rotor system or mast. If you held up the helicopter by its rotor system, the distribution of its weight — not just what’s inside it but its engine, battery, tail rotor, etc. — would determine how level it hung.

Take, for example, my R44. Its full passenger load is in front of the mast. Its fuel, engine, and heavy components are slightly aft of the mast. For this reason, if I’m flying solo (just one person up front) with low fuel, the helicopter would be a bit tail heavy. As I set down from a hover to the ground, the back of the skids would touch the ground before the front. In fact, the right back would touch first. That’s the lowest point closest to the center of gravity for that load.

The same applies to R22 helicopters. In fact, it’s often terrifying for student pilots to pick up into a hover after their flight instructor steps out when its time for that first solo flight. (Sure scared the hell out of me.) The helicopter feels as if it’s going to flip over backwards!

But stick a pair of fatties up front in my R44 and the CG will shift forward. In fact, if you have enough of a load up front, the fronts of the skids will touch first on landing. (I remember the first time I flew with my brother-in-law on board. I thought I was landing on a slope!)

Watch any helicopter take off or touch down and you’ll probably be able to tell where its center of gravity is.

Why CG Is Important

CG limitations are important for aircraft operation. For example, if you’re loaded with too much weight up front, the helicopter will tilt forward more in flight. When slowing down, stopping, or hovering, you might not have enough aft cyclic to counteract this forward tilt. Ditto for lateral or aft CG.

Remember, every aircraft control has a “stop.” That’s the limit to the control’s movement. You pull the cyclic back to slow down in flight. If you’re heavy up front, you may have to pull it back to simply hover in place. If you’re so front heavy that you can’t pull the cyclic back enough to stop the helicopter from moving forward, you have a serious problem — a problem with your CG or balance.

Want to see how far your controls will move? You should be checking their movement before starting up by simply moving each of the controls as far as it will go. The idea is to make sure none of them are stuck on anything or binding in any way. You don’t want to learn about a control problem when the engine is running, rotors are spinning, and you’re picking up into a hover.

You Can Be Under Max Gross Weight and Still Out of CG

What was bothering me about the comments on that AOPA blog post was that a few of the early commenters kept referring to CG and “weight and balance.” But the blog post was about gross weight. CG wasn’t discussed at all.

I didn’t address CG in my post because that wasn’t being discussed. In fact, it’s quite possible to load an aircraft out of CG and still be within max gross weight.

CG Calculation

This aircraft is out of CG but still within gross weight limitations.

Want an example? Here are the plotted points for a W&B calculation for an R44 helicopter with 4 good-sized people on board (190 and 250 up front; 190 and 145 in back). It’s a short flight, so only 16 gallons or about an hour’s worth of fuel is loaded on board. The total weight of the aircraft is 2408 — that’s nearly 100 pounds below max gross weight. But as the graph points show, this aircraft is out of CG — too much weight up front.

If you’re having trouble reading this, envision the pink line as the mast. Everything to the left is the front of the helicopter. Everything to the right is the back end of the helicopter. The blue box is the CG envelope for the aircraft, as determined by the manufacturer. In this example, the aircraft with and without fuel is loaded forward of the CG envelope. That’s a no-no.

CG Example 2

The same passengers as in the previous example, but with heaviest and lightest passengers switched. This load is within CG.

This situation is extremely easy to fix. Simply rearrange the passengers. While you can’t move the 190-lb pilot, you can move the fatty beside him. In this example, the 145-lb passenger in back has switched places with the 250-lb passenger up front.

Adding fuel might help, since fuel is loaded aft of the mast. But you couldn’t add much — you’re already pretty darn close to max gross weight.

Of course, both of these examples show only longitudinal CG — forward to aft. Lateral, or side to side, CG also needs to be calculated. As many of the commenters pointed out, they’ve created spreadsheets to perform these calculations for them. So have I — where do you think these two diagrams came from?

CG Example 3

Take the balanced load of the second example and top off the fuel tanks and you’ll get a situation like this.

Can you be over max gross weight and within CG? Technically, no. As these two diagrams indicate, if you’re loaded too heavy, the plot points will be outside the CG envelope. That means you’re out of CG.

But are you really out of balance to the point where you’ll run into control issues? I wouldn’t want to find out for myself.

Which is More Important: Weight or Balance?

I’ll always argue that you need to consider weight before you worry about balance. If you’re too heavy to fly within manufacturers max gross weight allowances, you’re too heavy to fly legally. Who cares about balance at that point?

So if you’re too heavy, it’s time to reduce weight. Leave behind some gear. Take less fuel. Leave behind the passenger who really doesn’t need to come along. Can the mission be flown with the load changes? If so, go the next step with the new load and do the complete CG calculations. Are you in CG? If so, you’re almost ready to go.

Almost? What else is there?

Performance, of course. I’ll discuss that in a future post.