What Is a Pitot Tube? The Pitot-Static System Explained

A pitot tube is a small forward-facing tube, usually mounted on the wing or nose of an aircraft, that catches the air rushing toward you in flight. It measures the pressure of that moving air — called ram or impact pressure — and feeds it to the airspeed indicator, which compares it against still-air pressure to show how fast you’re flying.

That one little tube is the front door to your entire airspeed system. And it’s part of something bigger: the pitot-static system, a set of plumbing and instruments that runs on nothing but air pressure — no electricity, no engine, no GPS. This article walks you through the whole thing — the pitot tube, the static ports, the three instruments they drive, and the failures that have ended real flights. We’ll keep it grounded in how the air actually behaves, because that’s the understanding that keeps you alive on a cold morning when ice is involved.

What is a pitot tube and what does it do?

A pitot tube is a forward-facing tube mounted on the aircraft — typically under a wing or on the nose — that captures the pressure of air moving toward the aircraft in flight. This is called ram pressure or impact pressure. The pitot tube routes that pressure to the airspeed indicator, where it becomes the basis for your indicated airspeed. The faster you fly, the higher the ram pressure.

Think of it this way. Stick your hand flat out a car window at 60 mph and you feel the air pushing against your palm. Tilt your hand so it slices the wind and the push nearly disappears. The pitot tube is like your flat palm — pointed straight into the relative wind, catching as much of that moving-air pressure as it can.

The aviation version is simple: a tube with a small front opening that faces forward into the airflow, connected by a line that runs back to the airspeed indicator inside the cockpit. Most pitot tubes also have a tiny drain hole at the bottom that lets out any water that works its way in — and as you’ll see later, whether that drain hole stays open changes how the system fails when the front opening ices over.

What is the pitot-static system?

The pitot-static system is the combination of the pitot tube and the static port (or ports), plus the plumbing and instruments they feed. It supplies pressure information to three flight instruments: the airspeed indicator, the altimeter, and the vertical speed indicator. According to the FAA Pilot’s Handbook of Aeronautical Knowledge (PHAK, FAA-H-8083-25C), this system operates entirely on air pressure, with no electrical power required for the basic instruments.

Here’s the division of labor. The pitot tube supplies ram (dynamic) air pressure. The static port supplies still (ambient) air pressure — the pressure of the air the aircraft is sitting in, undisturbed by the airplane’s motion.

Each instrument uses a different combination of those two pressures:

That table is worth burning into memory, because it explains every failure you’ll study. The airspeed indicator is the only instrument that needs the pitot tube. The altimeter and vertical speed indicator run purely on static pressure. So a pitot problem affects only your airspeed — but a static problem can throw off all three.

The static port itself is usually a small flush hole on the side of the fuselage, positioned where the airflow stays relatively undisturbed. Many aircraft have a port on each side and connect them, which averages out small pressure differences during slips and skids.

How does the airspeed indicator use the pitot tube?

The airspeed indicator works by comparing two pressures: the ram pressure from the pitot tube and the static pressure from the static port. Inside the instrument, a sealed diaphragm receives pitot pressure, while the case around it receives static pressure. The difference between those two pressures — the dynamic pressure — drives the needle. More difference means more airspeed.

When the aircraft sits still, pitot and static pressure are equal, the difference is zero, and the needle reads zero. Start moving and ram pressure climbs above static pressure. That growing difference is what the needle displays as indicated airspeed.

The colored arcs and lines on the face are your operating limits. On a typical light trainer like the Cessna 172, you’ll see:

Memorize the meaning of the arcs, not just one airplane’s numbers — every aircraft’s exact speeds live in its own Pilot’s Operating Handbook. The FAA defines the V-speeds behind these markings, referenced in PHAK FAA-H-8083-25C and the Airplane Flying Handbook (AFH, FAA-H-8083-3C).

One term you’ll meet on the written test: indicated airspeed is what the needle shows, calibrated airspeed corrects for installation and instrument error, and true airspeed is your actual speed through the air mass (which climbs as you go higher and the air thins). The pitot tube directly produces indicated airspeed — everything else is correction built on top of it.

What is the static port and why does it matter?

The static port is a small opening — usually flush with the fuselage skin — that senses the ambient air pressure surrounding the aircraft. It feeds that still-air reference to all three pitot-static instruments. Because the altimeter and vertical speed indicator use only static pressure, a blocked or damaged static port affects those two instruments as well as the airspeed indicator.

This is why static ports get attention on preflight. A bug, a piece of tape left from washing, even a wasp nest can block the port. The port is placed carefully by the manufacturer where the airflow stays undisturbed — so you should never plug it, paint over it, or wax it shut.

Many aircraft include an alternate static source for this reason: a cockpit valve that lets the instruments draw static pressure from inside the cabin if the external port clogs. Cabin pressure is slightly lower than outside static pressure in an unpressurized airplane, so opening the alternate source typically makes the altimeter read a little high and the airspeed indicator read a little fast. Your POH lists the specific corrections. As a last-resort backup with no alternate source, breaking the glass face of the vertical speed indicator exposes the static instruments to cabin pressure — it damages the VSI, but it beats flying blind on all three instruments.

What happens if the pitot tube gets blocked?

A blocked pitot tube causes the airspeed indicator to malfunction, and the exact behavior depends on what’s blocked. If only the front opening (the ram air inlet) is blocked but the drain hole stays open, trapped pressure bleeds out and the airspeed indicator drops toward zero. If both the inlet and the drain hole are blocked, the trapped air acts like a sealed column — and the airspeed indicator behaves like an altimeter.

That second case trips up a lot of students, so let’s slow down. With the pitot system fully sealed, the pressure inside the line is locked in. As you climb, the static pressure around the airplane drops, but the trapped pitot pressure can’t change. The instrument sees a growing difference between the two — so the airspeed reading rises as you climb, even if your actual speed is steady or falling. Descend, and indicated airspeed falls. The needle is now tracking altitude, not speed.

This is the trap that has contributed to real airline accidents, where iced-over or obstructed pitot systems fed pilots airspeed readings that didn’t match reality. The lesson: an airspeed indicator can lie convincingly, so cross-check it against pitch attitude and power setting.

Here’s the clean summary to lock in for the checkride:

The biggest real-world cause of a blocked pitot tube is ice. Which brings us to the heater.

Why does my airplane have pitot heat?

Pitot heat is an electric heating element inside the pitot tube that prevents ice from forming over the ram air opening and the drain hole. When you fly into visible moisture at or near freezing temperatures, ice can seal the pitot tube in seconds — and as you just learned, a sealed pitot tube gives you dangerously misleading airspeed. The pitot heat switch keeps the tube clear so the airspeed indicator keeps telling the truth.

This is one of the few parts of the pitot-static system that needs electrical power. On most light aircraft it’s a simple panel switch, and your checklist tells you when to use it — typically before entering visible moisture, in icing conditions, or as a standard instrument-flight item.

Test it on the ground the way your POH directs: with the master on, flip pitot heat on for a few seconds and carefully feel the tube warm up, then turn it off. Be quick — that element gets genuinely hot and draws a lot of current. A pitot tube that doesn’t heat up is a squawk worth catching on the ramp instead of in a cloud.

Understanding this system cold is exactly the kind of foundation the Angle of Attack Private Pilot Ground School is built to give you — instruments, systems, and the “why” behind every checklist item, taught so it sticks for day-one flying, not just for passing the written.

A cold morning in Alaska

Let me tell you about a preflight that stuck with me.

Early one winter morning up in Alaska, I was getting a 172 ready while a student stood next to me, coffee in hand, clearly wanting to skip ahead to the fun part — flying. The temperature was sitting right around freezing, and there was a thin film of frost on everything. We got to the pitot tube and I asked him to walk me through what he was checking and why.

He pulled the cover off, looked at the little tube, said “looks clear,” and started to move on.

I stopped him. I had him confirm the front opening and the drain hole were both clear, then walked him through the chain out loud: if that front hole ices over and the drain stays open, airspeed bleeds to zero. If both seal up, the airspeed indicator turns into an altimeter and climbs with you — which feels fine until you realize the needle has nothing to do with how fast you’re actually moving. Then we flipped on the pitot heat for a couple seconds and felt it warm.

The point I wanted him to feel, standing there in the cold, was that this isn’t a box to tick. The pitot tube is a tiny piece of hardware that quietly decides whether one of your most important instruments tells the truth. Up here, where weather turns fast and terrain doesn’t forgive a misread, that little tube earns your full attention every time. He never rushed a pitot check again.

PLT Study Guide

The FAA tags missed knowledge-test questions with Learning Statement (PLT) codes so you know exactly what to review. For a pitot tube and pitot-static system topic, these are the codes whose official FAA wording matches this material. (Heads up: PLT204 is “effective communication — basic elements,” which is a communication code, not a systems one. It does not apply to this topic, so don’t go chasing it here.)

PLT337 — Recall pitot-static system: components, operating principles, characteristics.
The core code for this article. Know the components (pitot tube, static port, alternate static source, drain hole) and the operating principle: pitot supplies ram pressure, static supplies ambient pressure, and the instruments respond to the difference or to static alone. Be able to predict how blockages affect each instrument.

PLT132 — Recall aircraft performance: instrument markings, airspeed, definitions, indications.
Know what the airspeed indicator markings mean: white arc (flap range), green arc (normal operating range), yellow arc (caution, smooth air only), red line (V_NE). Understand indicated vs. calibrated vs. true airspeed.

PLT278 — Recall indicating systems: airspeed, angle of attack, attitude, heading, manifold pressure, synchro, EGT.
Covers how the airspeed indicating system works as part of the broader set of cockpit indicating systems — specifically how ram and static pressure combine to drive the airspeed needle.

PLT167 — Recall altimeters: characteristics, accuracy.
The altimeter is a static-only pitot-static instrument, so expect questions linking static-source problems to altimeter behavior — including why a blocked static port or the alternate static source changes altimeter accuracy.

Frequently Asked Questions

FROM CHRIS

The pitot tube looks like the least important thing on the airplane — a little metal finger sticking off the wing. But it’s the front door to your airspeed, and airspeed governs almost every phase of flight. Understand the pressures, respect the failure modes, and never rush that part of the preflight. Master the small stuff and the big stuff takes care of itself.

Throttle On!

Chris Palmer

Founder & Chief CFI, Angle of Attack — Two-Time Master Aviation Educator and Gold Seal CFI