A Case for Weight and Balance Checks
(Originally published on January 9, 2019)
Feeling a little overweight; out of balance perhaps? Yes, holiday treats can sure take their toll on anyone’s waistline. But relax, we’re only talking about your aircraft.
And like people, our planes can gain weight over time. Oil, hardware, and other stuff eventually finds itself in the belly of the fuselage. These issues plus the occasional upgrade and modification will eventually cause a plane to be heavier than expected. This unexpected change in weight reduces the useful load of your plane and could pose a safety issue.
Here’s what you need to know.
Most planes that we see here at Sky Manor Air Repair are decades old. A quick review of a log book easily reveals many modifications and changes that have occurred over that time.
Computing these changes and entering it in the log book is an acceptable practice. However, faulty arithmetic and erroneous entries along with several negligible changes will present the owner with a false sense of useful load.
Some examples of modifications that can affect weight include:
- A new paint job
- Changing a battery to a new style
- Adding a new radio and other electronic device
- New headsets
- New cylinder probes – while it might only be a 2oz difference in weight each, when multiplied over 6 or 8 cylinders, you’ve now added another pound to the aircraft.
- A brand new custom interior can sure look beautiful. But it can also add a considerable amount of weight. Most often, the materials used to replace OEM coverings and sound proofing are heavier than those being replaced.
- New, thicker windshields are yet another example.
Negligible Weight Changes – A change so minor or insignificant to be deemed to have no effect on weight or balance.
A small modification can be individually managed in the log book as a negligible change. However, that which is negligible to one person may be different to another. Two ounces here, a few ounces there might not seem like much. But over time these ‘negligible’ changes can add up to significant differences in pound weight to your aircraft.
Proper Balance – it’s not just the weight, but where you’re carrying it
Upgrading your rotating tail beacon to a strobe might not seem like much. After all it’s only ½ pound lighter. Yet consider that it’s located at the farthest distance from the center of gravity and this ½ pound change can be exponentially more than that and may result in an aircraft exceeding its forward weight limit.
And we all know the consequences of too much tail weight in the event of a stall. Replacing the starter with a new light weight version can lighten the front of a plane by 8 pounds or more. Will this change affect the aft weight limits? It depends on the plane and any other modifications that may have been previously performed. However, you really wouldn’t know for sure unless you have it professionally checked
Useful Load – gross weight capacity minus the actual weight of the empty plane.
Adding weight to the aircraft is important as this will reduce its Useful Load. Think about loading your plane with baggage and passengers for your next trip, are you sure that you are not over the useful load rating for your aircraft?
A correctly weighed and balanced plane will give you peace of mind and ensure optimal performance when loaded with you, your passengers, and gear. Have your aircraft checked frequently.
So when’s a good time to do a weight and balance check?
Simple – whenever an appreciable change to the aircraft is made.
Aircraft used for commercial purposes need to be checked every three years as per FAR. Private aircraft have no such requirement. Although, if it has been several years and you have made a few mods, our advice is to get it done.
Sky Manor Air Repair and Avionics has the experience and equipment necessary to provide you with an accurate assessment of your aircraft’s W&B and provide professional advice on corrective action, if necessary.
Use good judgment. Protect your plane and yourselves by making sure that your aircraft is properly weighed and balanced.
Now, about those holiday treats?