Safety is simple. Use the right tool, the right person and the right procedures for the job. In well-maintained certified airplanes the right tool is usually there. The pilot presumably has been trained to fly the airplane and navigate competently.
Sometimes, however, the third leg of the safety stool is missing. The right procedures for most operations and even some emergencies are specified in the aircraft manual, but sometimes pilots arent familiar with the proper procedures, or sometimes they use procedures from other aircraft or other sources that arent proper for the aircraft and environment in which theyre flying.
Failure to use the proper procedures is an important finding in many aviation mishaps. It doesnt matter if the aviator is flying a general aviation aircraft, a military fighter or a commercial jet, knowing and using the proper procedures is crucial to flight safety.
No matter how skilled they are, pilots who pick the wrong time to execute a procedure that might be perfectly safe at other times can find themselves in trouble. Techniques that work in one plane may complicate matters in another. And sometimes published emergency procedures are either wrong or dont fit the emergency at hand.
Failure to follow the proper procedures is all around. Almost every pilot has been flying in the traffic pattern and suddenly had another pilot enter the pattern in a very non-standard manner, sometimes causing havoc. There are times and places where it takes standard procedures to ensure the safety of everyone.
Non-Standard Pattern Entry
In one accident, a C-54 (military version of the DC-4) air tanker and Beech Baron lead plane were on a fire suppression mission near the busy LA Basin. The air tankers mission was to drop red-colored retardant near fire lines, while the lead planes mission was to ensure the safety of the air tanker by checking out the stability of the air, checking for unseen obstacles and coordinating with ground fire fighters for the proper placement of retardant.
The lead plane departed the fire zone to return to the Ramona air tanker base about five minutes ahead of the air tanker. For undetermined reasons, the lead plane did not return to the Ramona airport at its usual speed and later was observed trailing the air tanker from above and to the left. The lead plane then appeared to accelerate during the descent to enter a nonstandard overhead traffic pattern at Ramona.
The 360-degree overhead pattern was similar to the type of landing approach used by military aircraft at military airports, however the airport had no approved procedures for using this approach. During the entry to the non-standard pattern, the Baron struck the air tankers vertical stabilizer.
The air tanker pitched upward to a near vertical nose-up attitude and then nosed down and descended uncontrolled. The empennages on both aircraft were separated and both planes entered an uncontrolled descent until impact. The lead plane descended in a flat spin. Both aircraft were destroyed, along with two residences, a water tank and two vehicles.
The NTSB determined that the probable cause of the accident was the pilot of the Baron had an inadequate visual lookout, and the operators procedures concerning the 360-degree overhead approaches were inadequate.
The non-standard 360-overhead pattern entry might work fine at a military facility where it is standard operating procedure, where aircraft enter the initial position from a standard direction, and where the aircraft share similar capabilities. That isnt the case at many civilian airports, where traffic can range from gliders to old taildraggers to corporate jets. The range of traffic pattern speeds for such a diverse group of aircraft is tremendous.
Aircraft can approach the airport from any direction and some patterns can turn into quite a mess even when everyone is using standard procedures. Flying non-standard patterns doesnt make the traffic flow any smoother or any safer.
Running Out of Runway
Sometimes a procedure thats correct for one aircraft is incorrect in another. For example, a 737-300 was approaching its destination at night with the copilot at the controls as the pilot flying. He briefed the captain on the approach and landing, and said that he would not use the autobrakes or reverse thrust. Instead, he would hold the nose up and keep the nose gear off the runway to decelerate the airplane with aerodynamic braking.
Aerodynamic braking is used extensively by pilots who fly light, high-speed tactical military aircraft such as the Northrop T-38 on long runways. For aircraft designed like the T-38, the aerodynamic drag at high speeds with the nose in the air is a more effective braking force than using the wheel brakes, particularly above 100 knots. The co-pilot accepted this notion and obviously thought it would also apply to a 737.
The captain approved the co-pilots plan. Had either of them consulted the aircraft operating manual, they would have seen that the manufacturer allows a long roll-out without the use of the autobrake system, but only if the roll-out is planned with idle or normal reverse thrust. The aerodynamic braking technique is not described nor authorized in any of the operators documentation.
Fortunately for this crew, the weather was clear and they executed a visual approach to the 11,475 foot long runway. The airplane touched down at the proper speed in the runway touchdown zone. As the copilot had briefed, he kept the aircrafts nose up, no reverse thrust was selected, and during the initial part of the roll-out, no brakes were used.
At 100 knots, the first officer lowered the nose wheels onto the runway. The pilots were looking for the turn-around area at the end of the runway and did not observe the runway-light color changes that would indicate that the airplane was nearing the end of the runway. The darkness and absence of illuminated structures rendered few visual clues from the surrounding environment that the aircraft was nearing the end of the runway.
At 50 knots, the captain felt uncomfortable and ordered the copilot to stop the aircraft. The first officer complied, but was unable to stop the aircraft in the remaining 413 feet of the runway. The airplane stopped with the nose wheels in the grass overrun and was damaged during the push back onto the runway with a ground vehicle.
Just why the crew decided to use a procedure that is unspecified in the operators manuals is unknown. While the procedure may have worked on the military jets the co-pilot had flown before, what led him to believe that such a procedure was equally applicable to a transport aircraft? The drag to weight ratio is far different in a T-38 than in a Boeing 737, and therefore the aircraft will behave differently during the land roll.
Professional pilots are expected to fly by the book, and this procedure clearly wasnt in the book. This is hardly an isolated occurrence. In a study of 94 accidents in transport jets from 1977 through 1984, fully a third involved the pilot deviating from established operational procedures.
Pilots love hangar talk, and one of the staples involves non-standard procedures. The conversation might go something like, My buddy flew off carriers in the Navy and he said they take off with the gear handle already in the up position, so thats what I am going to do. Is this a dangerous attitude? We dont know of a single aircraft manual that endorses starting the takeoff roll with the gear lever in the up position, and there are a number of things that can go wrong.
Flight Safety teaches that one of the classic warning signs of a developing error chain is using a non-standard or unpublished procedure. Basically, the bottom line is that it is safest to follow the prescribed procedures from official sources. Hangar talk, while its amusing and is sometimes informative, should never be taken without a dose of skepticism.
For starters, refer to official publications such as the aircraft flight manuals, company operations specifications if you fly commercially and the FAA publications. If you decide to explore deviations from approved procedures, go into it with your eyes open as to the potential traps that may be waiting.
One reason for exploring deviations is that sometimes the official sources dont address the particular scenario youre considering. In addition, sometimes the manual is just flat out wrong.
Which Procedures to Use?
Well-written aircraft manuals should specify the proper procedures for operating the aircraft. The problem is that not all aircraft manuals are well written, especially among older planes. However, even modern planes can have errors in the book that were never detected during flight testing. In fact, one crew discovered that following emergency procedures by the book in military turboprop created even more problems.
The pilots fly the military version of a common turboprop commuter aircraft. When they were back for their annual training in the simulator, they experienced a warning light for the generator. They properly delegated flying and non-flying duties, then started to diagnose the problem.
Official proper procedure called for the pilots to couple the generators. When the pilots did so, the entire electrical system became inoperative. Instead of having one operative busbar, both busbars were now shorted out and the crew was left without an operative DC electrical system in the aircraft.
They were now running on the backup battery and the emergency instruments, which allowed for a maximum of 30 minutes of electrical power. Thats not a good place to be. Luckily this occurred in a simulator, and that is how we discovered that the manual had a serious oversight in the emergency procedures.
The specified emergency procedure did not differentiate between simple generator failures and short circuits within the associated busbar. Rather, the procedure directed the pilots to connect the inoperative busbar with the other primary busbar. With a short circuit on one busbar rendering it inoperative, connecting the good busbar resulted in wiping it out, too.
The simulator training facility that trains most of the regional airline pilots in this aircraft recommended that we examine the emergency checklist used by the commuters.
Check airmen examined the emergency procedures and rewrote them as necessary, ensured that they complied with the FAA-approved operating manuals for other operators, checked with the manufacturer to assure its applicability. Those procedures have since been formally adopted.
This incident shows the optimal way to revise procedures. The pilots happened to discover that the manual had an oversight, and the proper authorities went through a process to ensure that the proposed modification was proper. Airlines expect their pilots to abide by the procedures, and there is no room within a reputable airline for variation from the approved procedures.
It boils down to the bottom line, Use the right procedure for the job. If you believe the procedure is in error, then its completely proper for you to question it and get it changed. In the interim, its generally best to fly by the book. Its a true mark of a professional aviator, regardless of the type of aircraft you fly.
You would be aghast to discover that your doctor had arbitrarily decided to try some new, untested procedures on you, and the same thing goes for aviation.
-by Patrick R. Veillette
Patrick R. Veillette is an ATP with more than 11,000 hours. He directs a research program studying human behavior in high-risk environments.