Know the Airplane
Once you start flying a particular aircraft you should start learning how it differs from the information in the POH. The POH data is for a new aircraft with the best of pilots the manufacturer could obtain. Begin by operating with the book figures. 
--Use radar or a GPS to obtain performance figures at 75% power. 
--Have the aircraft refueled after each flight and develop a consumption table for the flying you do. 
--Develop your own tool kit, as things need fixing. 
--Learn what is normal for this particular plane so you can become sensitive to such things as carburetor ice, an door ajar, a pending brake problem, control freedom, trim settings, seat problems, etc.

Reading FAR 91.9 says the aircraft must have an AFM/POH but FAR 21.5 says this is only required only for aircraft certified after 1979. All prior to 1979 aircraft may fly legally with placards. The only way to find out if an aircraft is required to have an approved manual aboard is to check the type certificate data sheet. This sheet is available at the local Flight Standards Office.

Aircraft structure has progressed from wood and wire to mild steel and chrome-moly steel. Along came aluminum alloyed with copper for strength, magnesium for resistance to corrosion and manganese for workability. The alloy can be clad with other metals to acquire any desirable quality. Pure aluminum is almost proof against corrosion. Titanium melts at 2700 degrees and is 60% heavier than aluminum while 50% lighter than stainless steel. Magnesium, with the highest strength to weight ratio of all aircraft metals, is 2/3 the weight of aluminum. Magnesium's drawback is that it burns explosively once reaching 1200 degrees. Synthetic composites and boron fibers are the present new kid on the block. Any rivet used must be compatible with the metals being joined.

The basic criteria used by the FAA for aircraft components of a critical nature is one failure in a billion flight hours. This high standard today is unreasonable when applied to aircraft of an older era with most parts nowhere close to this modern standard. The FAA is changing to allow a failure to flight hours at least equal to the system being replaced. Electronic ignitions will be replacing magnetos.

The aircraft is designed to crumple every place but the cockpit. Where conditions do not permit an obstacle free landing, you should select obstacles that will absorb impact. With secure and tight belts you will not bounce into the parts of the cockpit. You are far more likely to be injured by beating yourself against the inside of the airplane than in any other way. Some form of engine failure causes 1/4 of all accidents. Mechanical failure is the form least likely to occur. Running out of fuel is most likely.

Aerobatics
Performing maneuvers that the plane is not certified for is foolish and unprofessional. In aerobatics a little knowledge is dangerous. Aircraft safety margins exist but they are not large and usually apply to normal operations. Failure is apt to occur due to long-term fatigue or corrosion where the failure margins have been lowered. Even minor excess stress on an aircraft is accumulative. An aircraft that has been over stressed is just waiting for the next pilot to make it come apart. Every pilot flying a previously flown plane is subject to whatever has been done to the airplane before.

The shape of the structure determines much of the strength of an airplane. The slightest change in shape can greatly reduce aircraft structural strength. Proof of this can be demonstrated by using a soft drink can. A can can hold your weight if the shape is undamaged. A pinhole in the side can cause a can that once held your weight to collapse. When even a minor aspect of aircraft shape is changed the strength of that structure, it is no longer as certified.

It is the responsibility of every pilot to operate the aircraft in compliance with the restrictions and limits of the manufacturer's POH and placards. This requirement is part of the FARs Part 91.9.

GA Aircraft in Icing Conditions
FAR 91.9 requires obeying operating limitations of POH and placards. If operation in icing condition is prohibited then you cannot fly into known or forecast icing.

Aircraft Papers
No small aircraft built before 1979 needs a POH. Every younger plane must have an FAA Airplane Flight Manual (AFM) that is only issued for a specific airplane unlike the POH, which is for a large group of similar aircraft. If the POH has weight and balance data them it too, like the AFM must be aboard the aircraft. It is always a good idea to make periodic reviews of the manual information and recommendations for normal and emergency operations.

Weight and Balance
--A plane with weight at the rear limit of the envelope becomes unstable and will have difficulty bringing the nose down at very slow speeds such as a stall. 
--With the weight too far forward the plane becomes so stable that you might not be able to bring the nose up to land.

The range for an a particular aircraft is shown in the POH charts and is supplemented by the actual weight and balance papers required aboard the aircraft. Finding that the weight is in that range of the envelope is the "balance" part of the weight and balance problem.

Aircraft balance determines where the weight (fuel, people, baggage) is in the envelope. Each bit of weight is referenced to a station. Every station has an distance measured from the aircraft's datum point. By multiplying this distance by the weight placed at each station you obtain a figures called 'moment'. You add all the moments together including that of the aircraft and divide it by the total weight of the loaded airplane. In the weight and balance papers is a chart that you can use to determine if you are within balance limits. An aircraft can be under gross weight, but out of balance. Also, a plane can begin a flight within the envelope but be out of the envelope as fuel is used.

The balance part of the aircraft weight-balance applies to the balance distribution of aircraft weight. The aircraft must balance somewhere within the balance range and balance equation is as important as the weight of the flight envelope's longitudinal axis. Where it balances is called the called the center of gravity. By aircraft design there are limits to the ability of the center of gravity to move forward and backward. these limits are determined by the control effectiveness in maintaining pitch control at the slow-extremes of airspeed.

--Over weight and out of center of gravity limits makes an aircraft unairworthy
--General aviation's aircraft may not be individually weighed. Manufacturers fleet weight may be used.
--New installations require a new computation and 'superceded with date and certification of mechanic.
--AC120-27C makes change of less than one-half of one-percent of weight or C.G. reweighing exempt. (Thats .005 of gross weigh or 1/2 pound per 1000 poundst)
--Weight and balance records must (should) be part of the pre-purchase records.
--Each new weight will probably give a new C.G. location and range.
--Different manufacturers use different datum points.
--Gasoline weighs differently for different temperatures. At higher temperatures gasoline weighs less.
--Only at -7 Celsius does gas weigh 6-pounds per gallon.

Aircraft Loading
Average G. A. load is 1.7 people. Single engine aircraft are required to have a stall speed below 61 knots. A G.A. aircraft must be able to climb at gross with full flaps  Some C-172s have difficulty on a warm day or at altitude.  In later models of Cessnas the limit of 30-degrees flap extension allowed certification 100-pounds heaver than at 40-degrees flaps.

Baggage Security
--The actual weight of baggage limit is made low because of the potential G-loads possible on aircraft.
--A significant increase in G-force could damage the structure or cause an aft center of gravity.
--The security becomes important especially if moving baggage changes the C. G. of the aircraft.
--Never put something in the back of the aircraft that you may be needing in flight.

Continue To Next Page