SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/ifr-static-blocked-altimeter

Static ports ice over at 5,000 feet and you climb to 7,000. What does the altimeter show?

Frozen at the altitude where the blockage occurred.

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  1. It reads 7,000 feet as normal
  2. It drops to zero
  3. It stays frozen near 5,000 feet ✔

Why: Trapped static pressure cannot change as you climb. The altimeter therefore freezes at the altitude where the blockage occurred. If the airplane has an alternate static source, use it.

Huh, didn't know that: Preflight should include checking that static port openings are free of blockage and damage.

The dad joke
My altimeter froze at 5,000 feet. Talk about being stuck in the past.
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References

Answer: It stays frozen near 5,000 feet. Trapped static pressure cannot change as you climb. The altimeter therefore freezes at the altitude where the blockage occurred. If the airplane has an alternate static source, use it.

  1. FAA Instrument Flying Handbook (FAA-H-8083-15B) www.faa.gov/sites/faa.gov/files/pilots/FAA-H-8083-15B.pdf
    Trapped static pressure causes the altimeter to freeze at the altitude where the blockage occurred.
    Checked 2026-10-11.

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Test yourself in the game

FlyingIce blocks a pitot tube's ram opening and its drain hole. What does the airspeed indicator do in a climb?FlyingYour static system is blocked. What does the vertical speed indicator show while you climb?FlyingStatic ports block at 4,000 feet. You then climb well above that. How does the airspeed indicator read?

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