In real life: how important is the center of gravity in a 2 person plane

[oneleg]

What do real life GA pilots do to calculate the center of gravity? I can't imagine them weighting each luggage with a weight scale each time they take off.

[PhrogPhlyer]

17 minutes ago, oneleg said:

What do real life GA pilots do to calculate the center of gravity? 

GA pilots calculate a weight & balance for nearly all flights, In GA aircraft small changes can make a big difference to CG location, which then effects ability to rotate on TO, have a proper flare on landing,  recover from a stall/spin, and other safety of light considerations.

https://www.cfinotebook.net/notebook/aerodynamics-and-performance/weight-and-balance

 

 

[flytv1]

2 hours ago, oneleg said:

What do real life GA pilots do to calculate the center of gravity?

Hi.

The less power the more important the calculations are. And for a small GA it's very important to know the CG and weight. In some acft the CG can change during flight, by using fuel as an example, and you will have to take that into account.  Some planes you may not be able to land if the CG changed in flight and you did not take CG change into account.

There are also some Heavies when they are empty the have to be supported otherwise the tail may touch / hit the ground.

That said id you use the same plane, and are familiar with it, around 6 seats, you can easily calculate the CG and Take Off weight without having to check every item, if you know that you are below max weight.

The planes are designed to be flexible to an extent, unless you are looking / flying something very light / low power and or a high performance doing some unusual maneuvers.

[oneleg]

If the center of gravity (CG) is important, how can a GA plane like this guy //42 FreedomFox / Fox2 - Complete - Orbx (orbxdirect.com) be flown alone without a passenger? With the pilot only, the plane's CG is on the left side of the plane. I've seen tons of videos of other GA planes without passengers. What do single pilots do to keep a good CG when flying without a passenger?

[loki]

The pilot isn't that far laterally from the CG, so in most aircraft it won't make a big difference, maybe not even enough to be noticed. An imbalance in fuel tanks in the wings, however, would be more likely to cause problems as they are further away from the CG.

[nsproles]

2 hours ago, loki said:

The pilot isn't that far laterally from the CG, so in most aircraft it won't make a big difference, maybe not even enough to be noticed. An imbalance in fuel tanks in the wings, however, would be more likely to cause problems as they are further away from the CG.

I knew a Bell 47 Sioux pilot who was so light that he had to have a jerrican of fuel or water in the right hand pannier when flying without a payload, so as to avoid applying constant pressure on the pedal.

[nsproles]

10 hours ago, oneleg said:

What do real life GA pilots do to calculate the center of gravity? I can't imagine them weighting each luggage with a weight scale each time they take off.

I recall a take-off from a mountain airstrip in a Piper Aztec in Papua New Guinea that frightened the living daylights out of the pilot and I.  It may have been a good thing if he had used a set of scales to weigh everything he pushed on board.    In his own words 'I am never going to do that again!'

[budreiser]

This not a GA situation but a great example of CG importance:

 

Air Midwest Flight 5481 - Wikipedia

 

 

 

 

[PhrogPhlyer]

10 hours ago, oneleg said:

If the center of gravity (CG) is important, how can a GA plane like this guy //42 FreedomFox / Fox2 - Complete - Orbx (orbxdirect.com) be flown alone without a passenger?

Aircraft have a CG "range" laterally and longitudinally.

So dependent upon the aircraft, there may be very wide allowances with pilot/passenger and baggage locations.

[flytv1]

12 hours ago, oneleg said:

If the center of gravity (CG) is important, how can a GA plane like this guy //42 FreedomFox / Fox2 - Complete - Orbx (orbxdirect.com) be flown alone without a passenger?

Hi.

You can design an acft to fly with or without additional load with the CG in the proper envelop.

If designed to accept a load, the load better be in the proper place to keep it withing the CG envelop limits.

There are some some Heavy acft that in empty configuration cannot maintain level position on the ground and have to supported, then loaded in a certain sequence before you can remove the ground support. When finished loading that acft better be within CG limits or it's not going anywhere.

[oneleg]

MSFS shows the plane's LEMAC and TEMAC (Leading Edge and Trailing Edge Mean Aerodynamic Chord) - see image below.

 

A few questions about the image:
 

1. Are LEMAC and TEMAC useful when FWD and AFT limits are shown already?
2. How come there are no LEFT and RIGHT limits as there are for FWD and AFT?
3. Are CG limits usually posted in the pilot operating handbooks?
4. Are there two-seater planes which can't be flown without a passenger?
5. Are there FAA rules against flying off-center?  

Thank you.

[tiger1962]

1. Are LEMAC and TEMAC useful when FWD and AFT limits are shown already?

Leading Edge and Trailing Edge MAC are the FWD and AFT limits.

2. How come there are no LEFT and RIGHT limits as there are for FWD and AFT?

Left or Right weight imbalance can be compensated for by rudder and/or aileron trim - that's what they there for.

3. Are CG limits usually posted in the pilot operating handbooks?

Yes.

4. Are there two-seater planes which can't be flown without a passenger?

No. Ballast is used in several forms; in two-seater competition gliders for example it's water which can be jettisoned if required.

5. Are there FAA rules against flying off-center?

Fore and Aft, absolutely. You can lose your license and your liberty for causing an accident due to this.

[oneleg]

27 minutes ago, tiger1962 said:

1. Are LEMAC and TEMAC useful when FWD and AFT limits are shown already?

Leading Edge and Trailing Edge MAC are the FWD and AFT limits.

2. How come there are no LEFT and RIGHT limits as there are for FWD and AFT?

Left or Right weight imbalance can be compensated for by rudder and/or aileron trim - that's what they there for.

3. Are CG limits usually posted in the pilot operating handbooks?

Yes.

4. Are there two-seater planes which can't be flown without a passenger?

No. Ballast is used in several forms; in two-seater competition gliders for example it's water which can be jettisoned if required.

5. Are there FAA rules against flying off-center?

Fore and Aft, absolutely. You can lose your license and your liberty for causing an accident due to this.

Very nice answers, thank you. A follow-up on #1. If LEMAC/TEMAC are the FWD/AFT limits, why then are these figures shown separately on the image? Also, in MSFS once the FWD/AFT limits are exceeded, the color of the figures turn red way in MSFS before the limits for LEMAC/TEMAC are reached.

[loki]

1 hour ago, oneleg said:

2. How come there are no LEFT and RIGHT limits as there are for FWD and AFT?

 

To get into the physics a bit, check out the Wiki article below and note the effects of weight and distance on the moment arm. With GA aircraft the pilot and passengers are quite close to the centre and have low moment arm, and thus low effect on the balance. You also have the wings on both sides providing lift, minimizing the imbalance caused with only one person on board. The biggest issue would be constantly countering the imbalance with manual inputs or rudder and/or aileron trim, as Tim notes. The fore/aft balance of the plane, however, is much more critical with the relationship between the nose heavy design of GA aircraft, the centre of lift, and the tail balancing out the nose. There is also more opportunity to load passengers and cargo further from the CG, causing a bigger moment arm, and getting the plane outside of its design envelope.

 

https://www.wikiwand.com/en/Center_of_gravity_of_an_aircraft

[avallillo]

There are small scales with handles and hooks that make it easy to weigh anything that you put into an airplane.  Some things can be estimated, and others, such as the weight of passengers, can be taken on faith as reported by the individual (I would have said this only applies to men, but political correctness being what it is.....!)

 

Interestingly, at the airline level, standard weights are used for just about everything except the cargo.  The standard weight of adult males and females has had to be adjusted considerably upward twice in the last 60 years, so great has been the "supersizing" of the American public!  It all works out - other than a major shifting of cargo location on takeoff, I cannot recall an accident at a part 121 operation any time during my career that had, as a major factor, weight and balance issues.

 

As for two seat airplanes, if the seating is tandem - that is front and back - then there are probably a few that can only be flown solo from one seat or the other.  But with side by side seating, the seats are usually right on the cg anyway, and there is no penalty for occupying only one.

[tiger1962]

22 minutes ago, oneleg said:

Very nice answers, thank you. A follow-up on #1. If LEMAC/TEMAC are the FWD/AFT limits, why then are these figures shown separately on the image? Also, in MSFS once the FWD/AFT limits are exceeded, the color of the figures turn red way in MSFS before the limits for LEMAC/TEMAC are reached.

 

The figures will turn red because you've exceeded the Maximum Take Off Weight (MTOW) for that aircraft. Weight and Balance are two separate issues, but they are closely linked in aircraft.

[PhrogPhlyer]

1 hour ago, tiger1962 said:

5. Are there FAA rules against flying off-center?

Here's everything the FAA thinks you should know about W&B.

https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/FAA-H-8083-1.pdf

 

[oneleg]

Thank you all!

[Hyperdark]

Lol, how important?...in the little aeroplane I fly most I can alter the trim by leaning forward in my seat

[pzl 104]

On 11/25/2023 at 7:01 AM, oneleg said:

If the center of gravity (CG) is important, how can a GA plane like this guy //42 FreedomFox / Fox2 - Complete - Orbx (orbxdirect.com) be flown alone without a passenger? With the pilot only, the plane's CG is on the left side of the plane. I've seen tons of videos of other GA planes without passengers. What do single pilots do to keep a good CG when flying without a passenger?

That's one of the many serious bugs in all MS sims, P3D and MSFS. The CG effect is exaggerated a lot. That's especially noticeable with a left/right CG shift. 

3rd party devs can easily fix this by placing the pax, fuel etc. load much closer to the CG than IRL to achieve a realistic CG shift effect.

 

My airplane art:

Bernt Stolle - Art for Sale | Fine Art America

[chicagorandy]

This might be useful -  Weight and balance

[PhrogPhlyer]

28 minutes ago, chicagorandy said:

This might be useful -  Weight and balance

I'll definitely put this on my list of articles I need to do.

Probably write as I'm working on an E6B article.

Decisions, decisions... fly or write.

 

[oneleg]

On 12/10/2023 at 6:40 AM, PhrogPhlyer said:

I'll definitely put this on my list of articles I need to do.

Probably write as I'm working on an E6B article.

Decisions, decisions... fly or write.

 

Fly or write?

Solution: both! 

[oneleg]

On 12/10/2023 at 6:09 AM, chicagorandy said:

This might be useful -  Weight and balance

Thank you. So funny!

This one always makes me smile...