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The Aircraft You Fly Is Showing Its Age  
Considering the average age of general aviation aircraft you, the pilot, should expect and plan for a considerable difference between what the POH said about the aircraft when new and what will happen when it flies years later. The hazard of performance expectation and anticipation from the POH has become a continuous and ongoing flight problem.

--It is very unlikely that you will be able to lean for the performance climb and descent the factory pilot was able to obtain in your aircraft when new.

--There is no FAA effort to compare the new aircraft performance with the old aircraft performance. It is up to the individual pilot/owner to design and chart current performance tables in all the parameters.

--The exterior and interior of the new aircraft affects both appearance and performance. A crack, dent or bend can affect the damage resistance capability.

--Over the passage of years there has been an ongoing replacement of instrumentation and avionics. Hopefully, this has resulted in a net improvement, as would be the case of replacement of vacuum tubes by transistors.

--Although over the years many engines have been through TBO replacement the average aircraft is operating on a mid-time engine. The new factory engine is required to produce from 100 andl105 percent of design horsepower. There is no such requirement for any subsequent engine.

--There are no high altitude test requirements of G.A. aircraft. At high altitudes you may well be a test pilot.

--It was not until 1979 that G.A. aircraft were required to have a Pilot Operating Handbook specific to that aircraft as opposed to the traditional Flight Operation Manual for the whole model production line.

--It has not been uncommon that manufacturers would find way to fudge the performance numbers of their aircraft. When performance contests occur, some makes and models never win when held to the performance numbers of the manufacturer. (Cessna)

--Tests have shown that takeoff distances of older aircraft can be from 15 to over 40 percent longer.

--Time to climb times can be expect to require up to 50% more than book time.

--At cruise power settings you should expect to get at least 10% less than book speeds.

--The specific air range of an older aircraft (Speed and fuel consumption) can be 25% below book figures. Not only will it take longer to fly; it will take more fuel per unit of time flown.

--Any time you fly over three hours in an older aircraft you risk fuel exhaustion.

Pitot-Static System
This system gives a two-tier pressure to operate aircraft instrumentation. Static pressure uses ambient air that is protected from any movement influence. Pitot pressure is a measurement of ram air against a closed tube with a small opening into moving air. There is no airflow in either the pitot or static system. Blowing into either the static air hole or pitot tube can severely damage aircraft instruments. Blocked ram air into pitot can result in zero airspeed. Blocked static air will cause airspeed to increase during climb and decrease in a descent.  (Common PTS question)

Either system can be put into a failure mode by leakage or blockage. The smallest change in the integrity of an instrument or the tubing is hazardous. Most such changes cannot be visually ascertained as when I picked up a plane early one morning to ferry back to the home field after radio work. The aircraft had been parked out all night without the pitot cover. The morning was cool and sunny; the night had been slightly above freezing area wide but the aircraft was sheltered from the wind by a hangar.

Every thing was normal as I prepared to take off from a moderately short runway. A C-182-RG accelerates readily under a light load and I was airborne before I noted that the airspeed indicator was hardly reading at all. I believe that a smidgen of ice crystals was partially blocking the pitot tube. The blockage disappeared as I passed through 900 feet. What to do? Under similar conditions do a pitot heat check during preflight. It is best to keep these ports covered until readying for flight.

A blocked static port means that the altimeter needles will remain fixed except when turned by the Kollsman knob. The VSI would remain at zero. With only the pitot blocked and the airspeed indicator would operate only on static pressure. Lowering the nose would show a decrease in speed and raising the nose would give an increase indication. I have recently come across a situation where the alternate air was turned on in flight and never turned off.

When the static port blockage occurs in a situation where there is no change in altitude, as it would on the ground, the airspeed indicator will not be affected. Should your altitude increase you will get progressively lower airspeed indications. Where this problem exists, it is best to fly by power setting only.

Static Air Ports
The most favorable static port location is one that has neither positive or negative pressure. Manufacturers have become expert at putting static ports at the best location. The pressure on the static port can be influenced by the use of flaps, a slip, skid or yaw. The static port is located to minimize such maneuver influence. Some static ports have angled holes as part of the installation to help reduce maneuver effects.

Prior to location of static ports a drogue is flown behind the 'proof of concept' design to get an undisturbed reading to compare with various trial static air port locations. Some Pipers have the static air hole as a part of the pitot mast. Aircraft with autopilot, pressurization or electronic flight instrument systems will have independent backup static air systems to act as back up. Some static ports are heated. The alternate air control usually under or near the bottom of the instrument panel is designed for use when, for whatever reason, the static ports become fouled.

Airspeed Indicator
The airspeed indicator uses the differences between the static pressure and the pitot pressure to display airspeed. The pitot tube takes ram air pressure (not a flow of air) from aircraft motion to drive the diaphragm of the airspeed indicator. The static air hole(s) takes the ambient pressure of the aircraft and registers this pressure on the altimeter, the vertical speed indicator and the side of the airspeed diaphragm opposite the pitot's ram air side. The IAS requires both the pitot and the static to operate. The pitot tube usually has a heater element around it to melt ice as an obstruction. It would be useless against an embedded insect. Static system failure component by component or total is nearly impossible to detect during preflight. The functioning of the alternate static source is best checked during climb and descent for detecting a partially blocked system.

The airspeed indicator is color coded to show certain ranges of flight operation. White is flap range with Vso at the slow end and Vfe the high end. Cumulative damage will occur if flaps are lowered at speed higher than this range. The green range is normal with Vs1 as the gross stall speed without flaps. Where the green meets the orange is Vno listed as the maximum structural cruise speed. The orange range is to be avoided in turbulence. The high end of the orange range is capped by the red line. All warranties of structural strength are voided when speed meet or exceed the redline. All marked color codes are based on indicated airspeeds.

The airspeed will read slightly slower when you climb and slightly faster when you go down. If the pitot tube is blocked the airspeed indicator will work like an altimeter. As altitude is gained the IAS becomes greater than would be expected. As with the ear the airspeed works best which air pressure is equalized. There is no required inspection of the pitot-static system. There is a required inspection of the static system which involves the altimeter only.

Many need to know speeds are not shown on the airspeed indicator. Va the maneuvering speed at which warranties are voided if abrupt full control movements are made. Airspeed indicators since 1976 have been standardized as to panel location and to reading in knots with mph as an inner line of readings.

Airspeed Indicator
--Is a pitot-static indicator that provides pitch and power information
--The redline indicates the aircraft's Vne, the never-exceed airspeed.
--Yellow is a caution range which is avoided in turbulence
--the normal operating range is green as Vno
--The top of the green shows the maximum structural cruising speed
--Clean stalling speed is at the bottom of the green arc.
--The white arc indicates flap operating range
--The top of the white is the maximum flap extension speed, Vfe
--The Vso-stall speed is the landing configuration is at the bottom of the white arc.
--The clean landing speed is at the bottom of the green arc.
--The top of the white arc, Vfe, is the maximum extension flap speed.

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