Flying Aviation Articles

How CG Location Can Affect Airplane Performance

Hey everyone! I hope you all have had a good start to 2020, stuck to your resolutions, and greased all your landings so far. I heard a pretty good joke the other day that I wanted to share at the start of this post before we dig into some CG topics.

So we all know about Murphy's law right? It's very prevalent in aviation: anything that can go wrong will go wrong.

Well, here's how to get your friends on a good joke. 

"So you've heard of Murphy's law right?"

"Yes"

"Well have you heard of Cole's Law?"

"No what's that?"

"Oh it's just sliced cabbage with some dressing."

Love it! So cheesy but it's funny.

Ok now let's dig into some topics of the center of gravity.

First off: What is it? Well according to the Pilot's Handbook of Aeronautical Knowledge it is "the point at which an airplane would balance if it were possible to suspend it at that point."

Think about when you would get bored in elementary school and try to balance a pencil on your finger. Remember when you'd finally get it balanced, but it had to be a specific spot on the pencil or it'd fall back off? That's exactly what CG is on a plane. It's where most of the weight is concentrated, so once we load up the plane if it's within the CG then it flies the most stable and safe. It's also important to note that a CG is not just a fixed a point but it can move depending on the distribution of weight throughout the plane. 

But let's say we loaded the plane with too much weight or we didn't distribute it well and now we're out of CG limits. We can either be forward or aft (behind) that area. 

Forward Characteristics:

-Nose heavy

-Difficult to impossible to lift nose for takeoff

-Better stall recovery

-Total lift required by the wing is increased

-Wing flies at higher angle of attack, resulting in higher drag and higher indicated stall speed

Aft Characteristics:

-Tail heavy

-Difficult to impossible to recover from a stall

-Violent stall characteristics

-Light control forces that make it easy to overstress the plane

-Wing flies at lower angle of attack, resulting in lower drag and higher cruise speed

It's also always important to ensure to not take off past the max takeoff weight, and if you do it's brought down quickly/easily due to fuel burn. The effects of being overweight are dangerous. It includes:

-Higher takeoff speed

-Longer ground roll on takeoff and landing

-Higher stalling speed

-Reduced climb rate

-Excessive weight on the landing gear that can cause a collapse

-Accelerating metal fatigue over time

These characteristics run for all planes too, whether you're flying a Cirrus SR-22 or a King Air A100 you never want to be overweight or out of CG.

When it comes to weight and balance there is also several important terms to know that we use in order to help us calculate properly. These include:

Arm: horizontal distance from the datum line to the CG of an item (measured in inches)

Datum: an imaginary line from which all horizontal distances are measured in order to balance the aircraft. This is picked by the manufacturer and is usually somewhere like in front of the engine firewall or the leading edge of the wing. 

Basic Empty Weight: the standard empty weight of the plane and any optional equipment installed

Standard Empty Weight: the weight of the airframe, engines, permanently installed items in the airplane, unusable fuel, full operating fluids and oil.

Moment: this is the product of weight x arm and is considered to be the force that causes an object to rotate.

If you're ever trying to remember these and study some more check out chapter 10 of the Pilot's Handbook of Aeronautical Knowledge and your own operating handbook for whichever plane you're flying. There's always so much to talk about with weight and balance but if you remember anything know this: don't ever land overweight and never accept an aft CG! That's the two most dangerous scenarios. 

Anything else to add about weight and balance? Drop it below!

Tips for Noting the Wind on Ground Reference Maneuvers

Here's a short scenario:

You've just taken off from your home airport. You fly about 25 nautical miles out from where you took off and go find an area to do ground reference maneuvers.

Once you find an area you like you begin to get yourself set up to do your first maneuver: rectangular course for example. For rectangular course you have to enter it with a tailwind just like you would enter a typical traffic pattern. So now it's time to note the wind.

First rule: don't just use the direction the winds were at back at your home airport.

But it's just 25nm away, they should be the same right?

Wrong!

The winds can actually be blowing a completely opposite direction than they were back at the airport. This can be due to surface friction, the terrain of the area you're in, and of course what the weather is like for the day. If one area has thunderstorms blowing in the winds can be gusty and shifting, while 20nm away they're calm and skies are clear.

Remember this, especially on a check ride, when it comes to noting the winds. 

So, if you're just over an area with a bunch of fields and no airport to report the weather how do you find the wind direction?

Very simply: look outside.

Now, obviously you cannot truly see wind. But, you can see objects that it's blowing and the direction they're facing.

A great example would be the references that I use since I fly in Houston: refineries. The stacks are almost always blowing steam from the top and it's very easy just to glance at them and see which way the wind is blowing it.

Some other outside visual references would be trees, water, smoke if there is any fires out etc.

If there isn't any references to use and you have an avionics system on board, bring up the groundspeed display. You can always look at this and fly a 360 degree turn to set up for the maneuver and check where you groundspeed is fastest and where it is slowest.

This will tell you exactly where your tailwind is and where you have a headwind, so you can calculate from there how to enter the maneuver.

Using groundspeed also tells you a rough estimate of how strong the wind is blowing, so you can have an idea of how much correction you'll need during the ground reference maneuvers to hold your track. The bigger a difference between your slowest and fastest groundspeeds, the stronger the wind likely is.

Have any other tips you've found for your maneuvers? Drop them below!

We hope you're getting in the Christmas spirit this month, head over to Globalair.com to check out our cool Santa hat on the logo and see what's available on our website!

 

How to Determine Your Pivotal Altitude

Whether you're working on your commercial certificate now, going to be, or already have then you'll find this useful.

As part of the Commercial ACS, we as pilots have to learn Eight's-on-Pylons. This is a maneuver in which the plane flies around two pylons maintaining a visual sight reference with each one in relation to the lateral axis of the airplane. Drawing the plane's ground track, it looks like a figure 8, thus the term Eight's-on-Pylons. 

Picture from the Airplane Flying Handbook

One of the most important concepts to take from this maneuver is pivotal altitude.

So what is it?

Pivotal altitude is the altitude at which, for a given groundspeed, the projection of the visual reference line to the pylon appears to pivot. Simply put, it's what the plane keeps coming back to each time you're able to maintain the pylon off the wingtip and hold it. 

This is also something that is calculated before the maneuver is begun using the airplane's groundspeed. It's the groundspeed squared divided by either 15 for miles per hour or 11.3 for knots. 

Some things to note about pivotal altitude is it does not change with the angle of bank, given that it is not steep enough to affect the groundspeed (but if you do the maneuver and correct for wind properly you shouldn't have to over-steepen the bank where this happens). 

Pivotal altitude can be noted very easily while flying around the pylons. All you have to do is get the plane stabilized where you're holding the pylon off the wingtip with no pitch up or down correction, then look at your altimeter and note the altitude! This is what the plane will keep coming back to. 

You should also enter and exit the maneuver at the pivotal altitude; how close or far you are from it when exiting can exhibit how well the maneuver was performed. 

If you're needing help with commercial maneuvers, or just want to pursue a commercial certificate, take a look at our Aviation Training Directory to find somewhere near you to train.

Best of luck with your Eight's-on-Pylons and happy landings!

-Addi

 

The Aviation Spark

Nicole Lund

 

My sister, Lauren, in the pink and me in the blue.

 

The question I am asked most often is "how did you get involved in aviation?". Most student pilots have parents or relatives that are pilots who helped them get a foot in the door. However, I do not come from a family with a background in aviation. So, where did the spark to become a pilot come from?

The first time I flew on an airplane, I was four years old and on my way to the happiest place in the world, Walt Disney World. I remember boarding the plane and the captain giving me a pair of plastic pilot wings that I wore with a giant grin across my face. I was completely blown away by seeing the world from 35,000 feet. Growing up, my mom took me to a local airshow at Offutt Air Force Base. This sparked an interest in serving the country. There was a C-17 at the first Defenders of Freedom Air & Space Show that I went to. I could not fathom how a plane of that size could fly. I ended up touring the inside of the C-17 and that was when I realized that I wanted to be a pilot.

 
A photo I took of a C-17 from Travis AFB on an overnight at KOMA.
 
 

I felt embarrassed and ashamed for wanting to become a pilot. I had never met a female pilot. I did not start telling family and friends that this is what I wanted to do with my life until high school. I tried easing my family into the idea by mentioning how I wanted to join the Air Force. Then I slowly started bringing up the idea of wanting to fly. Needless to say, my family and friends thought it was just a phase. In high school, I was a 4.0 student as well as a varsity athlete in cross country, track and field, and trapshooting. I focused on my grades and extracurricular activities so that I would be competitive for an Air Force ROTC scholarship. My senior year of high school I was overjoyed by the news of receiving a Commander's Scholarship for the local detachment at the University of Nebraska Omaha (UNO). It was a full ride scholarship to study Aviation, I had my life planned out, so I thought.

My freshman year at UNO I juggled being a cadet and studying Aviation Management. At the end of my freshman year, I was crushed by the news that I had been medically disqualified from military service. That was a hard pill to swallow, but I knew I still wanted to fly. I ended up passing my first-class FAA medical and then began my private pilot training. I am now finishing up my commercial certificate with my eyes on a career in business aviation or with an airline.

Standing in front of a Citation Excel.

 

Tips For Renting Your Aircraft

Renting your Aircraft

If you own an aircraft and are not utilizing it as much as you would like or if you would like to try and recover some of the cost of owning the aircraft, you may have thought about renting your aircraft to other pilots. As a practical matter, that makes some sense. But before you actually rent your aircraft to another pilot, here are a few things you should consider.

Aircraft Owners May Rent Their Aircraft To Third Parties

It is important to understand that the FAA does not prohibit aircraft owners from renting their aircraft. In fact, the regulations specifically contemplate rental arrangements. So, renting your aircraft is permitted, provided that you comply with applicable regulations. The FAA provides guidance on what is and isn’t a permissible rental arrangement in Advisory Circular 91-37B Truth in Leasing (although truth in leasing requirements only apply to large civil aircraft, the general lease concepts discussed in the AC apply to leasing arrangements for all aircraft).

Make Sure Your Insurance Permits Aircraft Rental

Most aircraft insurance policies will extend coverage to other pilots who fly your aircraft provided that the pilots are either expressly identified in your policy or if they have the necessary experience/qualifications to meet the “open pilot” clause of the policy. However, if you are going to charge the pilot for use of your aircraft, you need to confirm that your policy allows you to rent or lease your aircraft to a third-party. Most aircraft policies issued to owners for personal/business flying do allow aircraft leasing, but it is important to confirm this with your insurance underwriter.

Also, rather than paying to obtain their own insurance policy or renter’s insurance to cover their use of your aircraft, most renter pilots will want to be named as an additional insured under your policy as this can oftentimes be done at no cost to you or the renter pilot. In that case, renters will typically ask for a certificate of insurance that reflects not only that they are added to your policy, but that they are covered for their operation and use of their aircraft. This is important because it doesn’t do the renter pilot any good if he or she is added to the owner’s policy but only covered for the owner’s operation of the aircraft, rather than his or her own use.

Renting Your Aircraft Can Trigger Tax Consequences

In most states, when an aircraft owner rents an aircraft to a third-party the owner is required to collect and remit sales tax on the rent paid by the third-party for the aircraft. If you are in one of those states, in order to rent your aircraft you will need to obtain a sales tax number so you can collect and remit sales tax to the taxing authority. This is the aircraft owner’s obligation and the taxing authority will hold the aircraft owner responsible for any sales tax the taxing authority believes the aircraft owner should have collected and remitted, regardless of whether the renter pilot actually paid the sales tax to the aircraft owner.

Also, when you rent your aircraft many taxing authorities view that activity as commercial activity which then means your aircraft could be subject to assessment of personal property tax on the value of the aircraft, or some portion of the value based upon the pro-rata rental versus personal use of the aircraft. Although not all states assess personal property tax on aircraft, if you are in a state that does you will want to determine your potential property tax exposure before you decide to rent your aircraft.

Conclusion

Although you will also have other things to consider as you decide whether to rent your aircraft to other pilots, these three issues should be near the top of your list. And if you understand and address these issues up front that will help ensure a successful aircraft rental experience for both you, the aircraft owner, and your renter pilot.

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