PA -18 Weight and Balance mystery solved
Piper PA-18 Super Cub · Weight And Balance
Overview
This document serves as a guide for understanding the weight and balance calculations specific to the Piper PA-18 Super Cub. It outlines essential terms and formulas necessary for determining the center of gravity (CG) of the aircraft. The document emphasizes the unique aspects of the PA-18's design, particularly the location of the datum and the implications for weight and balance calculations. It is aimed at pilots and aviation enthusiasts who need to perform weight and balance checks on the PA-18, ensuring safe operation within the aircraft's CG limits.
- The PA-18's datum is 60 inches ahead of the wing leading edge.
- At max gross weight of 1760 lbs, CG range on floats is 16.2 to 20 inches aft of the wing leading edge.
- At 1410 lbs, CG range is 11.1 to 20 inches aft of the wing leading edge.
- Total moments divided by total weight gives CG; subtract 60 inches to find the actual CG position.
- CG limits vary with gross weight; for example, N645DT's gross weight is 2000 lbs.
Document
Source
Originally published by alaskafloatratings.com. Sprinkle hosts a reference copy with an added summary, specifications and searchable full text.
Document details
- Type
- Weight And Balance
- Pages
- 3
- File size
- 424 KB
- Publisher
- alaskafloatratings.com
Specifications & performance
Extracted from this document.
Specifications
- Max takeoff weight (lb)
- 1,760
Weight & balance
- Cg range (in)
- 16.2
- Max takeoff weight (lb)
- 1,760
Common. Rarer than 8% of the aircraft models we track.
Most owners only have the POH. Here's the essential set for the Piper PA-18 Super Cub.
Free — save the PIPER PA-18 Super Cub to your watchlist and track it in one place.
More Piper PA-18 Super Cubmanuals & documents
See all 30 →- Airworthiness Directive Schedule Aeroplanes Piper PA-18 Series (Super Cub)Airworthiness Directives
- AAIB Bulletin: G-CUBX AAIB-30327Other Documents
- Final Report: Ground Assessment of Electronic Conspicuity DevicesOther Documents
- Supplemental Type CertificateFlight Manual
- Flight Test Instrumentation System for Small UASOther Documents
- PIPER PA-18/PA-12 PRODUCT & MODIFICATION GUIDEFlight Manual
- Type Acceptance ReportOther Documents
- Airplane External Load Operations Within the State of AlaskaType Certificate
- Piper PA-18 Super CubSystems Description
- ICA Maintenance Manual for 2200 Floats on PA-18 Piper, Super Cub modelMaintenance Manual
- Model 8400 brake booster assemblies and modification of Scott Aviation Model B-711 Brake Master CylindersSupplemental Type Certificate
- SERVICE BULLETIN No. 0 0 0 3Service Bulletins
If you fly the Piper PA-18 Super Cub, you may also be researching these.
In this document
Weight and Balance Basics
The document begins by defining key terms related to weight and balance: Weight is the amount in pounds an object weighs; Arm is the distance in inches from the Datum; Moment is calculated by multiplying Weight by Arm. The total moments divided by total weight gives the center of gravity (CG).
Datum and CG Limits
The PA-18's datum is located 60 inches ahead of the wing leading edge, which complicates CG calculations. The document provides specific CG ranges for the aircraft when loaded on floats, detailing the limits at different weights.
Calculating CG for the PA-18
To determine if the aircraft is within the proper CG range, one must subtract 60 inches from the calculated CG after dividing total moments by total weight. The document provides examples using specific aircraft weights.
Safety notes
- Ensure calculations are accurate to maintain safe CG limits.
- Always refer to the specific aircraft's gross weight when determining CG range.
Full document text
Another Back to the basic’s lesson: PA -18 Weight and Balance mystery solved Note: Before attempting to work a Weight and balance on a PA-18 you need to refresh your memory with these basic terms. Weight: Simple, it is the amount in pounds an object weighs Arm: Not the one extending from you shoulder. It is the distance in inches measured from the Datum Moment: Is not a measurement of time. I.e. “Just a moment.” It is the product of multiplying the “W” (weight) “X” (times) the “Arm” = Moment Hence the formula: W X Arm = Moment. Total of all Moments added together, Divided by the total weight = “CG” (center of Gravity) Datum: Is the point in space that the measurements for the arms are located. It can be located where ever the manufacturer decides. You are used to Cessna’s and other airplanes CG charts that simplify this issue of Weight and balance. Piper, in its infinite wisdom, decided when designing the Super Cub (PA-18) to place the Datum 60” ahead of the “Wing leading Edge” Then to add confusion the CG limits or range are in relation to the Wing Leading Edge. For N917VK the CG ranges on floats @ max gross weight of 1760 lbs. is 16.2 inches to 20 inches aft of the wing leading edge. At 1410 lbs. it is 11.1 inches to 20 inches aft of the wing leading edge. Bottom line, for you to understand the PA-18 weight and balance solutions. Always, after dividing the total moments by the total weights, subtract the 60” inches from that number to determine if your aircraft is within proper CG range. Note: The CG range varies with the gross weight of the PA-18. N917VK’s gross weight is 1760 lbs. N645DT’s gross weight is 2000 lbs. An STC from Whipaire the manufacturer of Whipline Floats make this possible.