Welcome Guest. Sign in or Signup

1 Answers

Altimeter density error

Asked by: 3387 views , ,
Aircraft Systems, Commercial Pilot, Flight Instructor, Instrument Rating, Private Pilot, Student Pilot

I understand that the Altimeter operates with the static system with the relative changes of pressure that inflates a wafer that turns the linkages of the needle. High to Low look out below.. Low pressure usually is cold air and is more dense with less kinetic energy.

My question...  Is it because there are more air molecules going in the static port that inflates the wafers more which indicates a higher indicated altitude?

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

1 Answers



  1. Brent on Jun 02, 2015

    I think you have the relationship between the wafer and the pressure backwards. As pressure increases, the wafer deflates. Decreasing pressure means the wafer inflates. Think of the wafer as an inflated balloon trapped in a jar. In this analogy, the air in the jar represents the pressure inside the instrument let in from the static port. The size of the balloon is the balancing point between the force of the pressure inside the balloon pointing out versus the pressure in the jar pointed inward on the balloon. If you increase the pressure in the jar (more air molecules) then the force inward on the balloon increases and the balloon gets smaller. Letting air out of the jar has the opposite effect on the balloon.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes


The following terms have been auto-detected the question above and any answers or discussion provided. Click on a term to see its definition from the Dauntless Aviation JargonBuster Glossary.

Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.