Welcome Guest. Sign in or Signup

2 Answers

Blocked Pitot / Static Drain Hole

Asked by: 14078 views , , , ,
Aircraft Systems, Instrument Rating, Student Pilot

If the drain hole is blocked but the inlet remains open how will your pitot/static instrument be effected and why?

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.

2 Answers



  1. Nathan Parker on Jun 10, 2011

    The textbook answer is that it shouldn’t affect any of the instruments.  The only time the drain hole blockage has any effect is when it’s combined with an inlet closure.  When the inlet is closed, the status of the drain hole controls whether the total pressure in the pitot tube is maintained, or drops to ambient static pressure (or less).
     
    I would bet, though, if we had instruments sensitive enough, we’d see a small gain in total pressure with the drain hole closed, with a minute gain in indicated airspeed.

    +4 Votes Thumb up 4 Votes Thumb down 0 Votes



  2. Wes Beard on Jun 10, 2011

    Nathan is correct!  I would like to add to the discussion the purpose of the drain hole.  Originally designed to allow water and other small FOD (foreign object debris) to escape the pitot system so that normal operation would not be impeded. 
     
    With that in mind, a blocked pitot drain hole won’t have any effect initially on the flight instruments.  Over time water and FOD will block the pitot ram air input causing erroneous airspeed indications.

    +2 Votes Thumb up 3 Votes Thumb down 1 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.