How to respond when systems fail
Modern Technically Advanced Aircraft (TAA) are loaded with systems intended to help keep the pilot alert, aware of his or her surroundings, and ready to address an emergency. Unfortunately, this robustness also implies a responsibility on the pilot's part to know and understand all of these systems so that they are properly utilized in the event of an emergency.
We must anticipate that things could go wrong, and we should prepare for these as best we can. Nobody starts out on a flight wanting something to go wrong, but that does not stop it from happening when you least expect it.
System failures can be placed into a number of categories. Abnormal conditions and emergency conditions are the two most commonly used. There is usually a checklist for each type of anticipated failure within each category. Just because the aircraft manufacturer considers an occurrence as an abnormal situation does not mean that it's not an emergency when it happens to you. You are the pilot in command, and you'll determine how to handle it.
| Loss of the primary flight display presents the pilot with a blank screen. What you must do to troubleshoot the problem depends on whether you're flying an Avidyne Entegra or Garmin G1000 system. Remember to keep looking outside while you investigate the problem. |
| If a failure occurs, stay calm. Reach for the checklist, control the aircraft, and start a logical troubleshooting process. Failed screens could be caused by something as simple as a bumped cabin light knob, or it could be something more complicated. |
| If the odds are against you, consider your closest landing options by pushing the "nearest" (NRST) button on your GPS. |
Time normally is a critical factor in emergency response. The longer a pilot waits after first discovering a problem, the greater the likelihood that it will get worse. Pilots have become so distracted while addressing a failure that they lose control of the aircraft. Don't be one of these statistics. Involve others. Inform air traffic control of your predicament. Pull out the pilot's operating handbook. Do whatever you have to do, but don't wait and hope that the situation will get better on its own. It won't.
You can do a number of things to prepare for the unexpected so that your ability to react appropriately is bolstered by experience. One of the things that can help is a thorough knowledge of emergency responses to challenges that can arise in the TAA cockpit. These systems are computers running software, and this software depends upon a whole host of sensors and signals from other devices to provide a fully operational experience. It stands to reason that there is risk of failure in more ways than might be expected from a conventionally equipped aircraft. Manufacturers of TAA have spent considerable time and money convincing the FAA that their systems are dependable, but the FAA has been watching "dependable systems" fail for unexpected reasons for many years.
Power problems
One of the most common problems that any pilot can experience is a failure of an alternator or loss of electrical power. Since just about every TAA aircraft comes equipped with two batteries and many come with a back-up alternator, one would imagine that the risk has been mitigated by the manufacturer. This is only partially true. Many of these systems are designed to only provide an electrical backup for a portion of the electrical system, not all of it.
The electrical system is divided into what are referred to as electrical busses. These busses are literally a subdivision of electrical components or appliances that are powered from a common set of circuit breakers. An example is an avionics bus. With the push of an avionics master switch, power is applied to a set of circuit breakers, allowing power to flow to all of the appliances attached to that bus.
Aircraft typically have at least two busses in the electrical system: main and avionics. TAA aircraft are typically divided into three: essential bus, a main bus, and an avionics bus. Pilots need to understand how these components function and interrelate in order to be able to respond to a failure or degradation. A technically advanced aircraft will typically send power to all the busses when the battery and the alternator are functioning properly. Should a failure occur such as the loss of an alternator, the aircraft will need to be reconfigured so that the main battery is not being used to power the entire aircraft.
A TAA such as a Cessna uses a smaller 24-volt battery to serve as a back-up for the essential bus in the event of an alternator failure. This is great, but the pilot must know that if all other power was exhausted from the remaining main battery, the standby battery can only power the essential bus and cannot provide any power to the main bus. What this means is that if a pilot exhausts the main battery after an alternator failure, the back-up battery cannot power any lights, flaps, fuel pumps, pitot heat, or any avionics that are not connected to the essential bus. Oops. This information would be helpful to know when planning a night flight. It would be better to exhaust the back-up battery first and then re-engage the primary battery for the landing so flaps and lights could be used at the end of the flight. This information is hidden in the POH.
PFD failure
Another emergency is the loss of the primary flight display (PFD). On an Avidyne Entegra or a Garmin G1000, the loss of a PFD will manifest itself in the same way--a black screen--but must be handled differently. Why? In both cases, the PFD contains all primary heading and pitot-static related information such as airspeed and altitude. It also contains the primary information on the horizontal situation indicator (HSI) that the autopilot uses to follow the flight plan. A G1000 has a failover mode that automatically sends the PFD information to the multifunction display (MFD) in the event of a sensed PFD failure, and it has a red reversionary button that allows the pilot to do this on purpose. This means you simply have to look over to the MFD and continue to fly the aircraft.
A total failure of the PFD on an Avidyne Entegra-equipped aircraft means the pilot is forced immediately to refer to the standby instruments, especially if flying at night or under instrument flight rules. There is no red button. In this case, the pilot may use the Garmin GNS 430 to control the autopilot and continue to fly the flight plan for the trip, but has lost the PFD display information, perhaps for the rest of the flight. Make sure that you put the autopilot in GPS steering mode by pressing NAV twice. If the PFD on the Avidyne has failed and cannot be brought back to life by a quick restart (pulling the circuit breakers--yes, there are two--and resetting within 10 seconds), it is recommended that the pilot pull both circuit breakers to the PFD and isolate it completely. Remember that the autopilot is following the CDI needle on the HSI and in this case, the pilot does not know what the HSI is saying because it can't be seen. Follow the checklist. It contains the tested procedures for most kinds of failures that the pilot could encounter.
Autopilot anomalies
Another failure that can occur on these aircraft is a failure of the autopilot or the trim system. In July's installment ("Glass Class: Automated Flying"), we talked about the autopilot and the fact that it consists of a control box and a number of different interfaces to servos and the TAA PFD screen itself. So there's a broad variety of potential for the system to misbehave. Pilots should monitor the autopilot for problems. Typically, small red lights illuminating "P" for pitch, "R" for roll, or "PT" for pitch trim--or any kind of flashing indication on the control head or along the top of the PFD--is an indication that "George" is in trouble. Sometimes you can restore the system by turning it off and then reinitializing it. Sometimes turbulence can throw the pitch channel into a tizzy, and a circuit breaker pull may be the only remedy. The pilot should know the autopilot systems cold and can practice overpowering the system manually in the event of a runaway servo. Instructors should practice autopilot stall recoveries with students to make sure they can recognize and recover from an autopilot-induced stall.
When a failure like this occurs, there are things pilots can do to help themselves. First, try to reset the component. Sometimes this can be done by resetting a circuit breaker, and sometimes there is another way to reset the component through a software switch.
It's important to be methodical and stay calm. When a failure strikes, reach for the checklist, control the aircraft, and start a logical troubleshooting process. Try to figure out exactly what happened. Find out if it is something simple. Failed screens could be caused by a bumped cabin lighting knob, or it could be something more complicated. Eliminate the simple explanations first. Don't become involved in trying to troubleshoot something that is unimportant to your flight.
Breaker basics
If a circuit breaker pops, is there smoke? If so, then the game is over; forget the component until you are on the ground. Don't try to reset a component that is popping a circuit breaker because it could start a fire. I have seen breakers pop because of a failure in the breaker itself. If there's no smoke, you are allowed a single attempt to reset a breaker of a needed component.
If it pops right back out again, then forget it. Fly the aircraft and start considering your options. If you just departed on your trip, consider returning. If you are almost to your destination, consider your risks of continuing to that destination with the degraded systems. If the odds are in your favor, then so be it. If the odds are against you, then immediately consider your closest alternative by pressing the "nearest" (usually NRST) button on your GPS. When selecting an alternative airport, consider whether that airport offers sufficient services to repair your aircraft.
In a true emergency such as an engine failure, low fuel warnings, or warnings related to oil temperature and pressure or fuel pressure, consider that the nearest airport may be your only option. Don't pass up a perfectly good airport only to make a landing on a highway in a field later.
Preparation is key
You should now have a better understanding of the emergencies a pilot needs to be prepared for in an aircraft equipped with a glass cockpit such as the Garmin G1000 or the Avidyne Entegra. The pilot must learn the procedures for addressing a variety of system failures and must become completely skilled at emergency operation modes. Flight instructors must test pilots' ability to respond quickly to a variety of issues. A good instructor should always question the student about potential failure scenarios.
A good scenario starts with the word suppose. You'll find that the skillful response to potential emergencies will be predicated on continual review of the POH and the checklist. A lucky pilot may spend an entire flying career without suffering a catastrophic failure, but a skillful pilot will spend an entire flying career preparing for the day when luck runs out. I would rather be skillful than lucky any day.
Michael G. Gaffney is president of Skyline Aeronautics at Spirit of St. Louis Airport in St. Louis, Missouri. A Master CFI and a Master Ground Instructor, he was named the 2007 national Flight Instructor of the Year. Gaffney, author of ASA's The Complete G1000 Course, also holds airline transport pilot and airframe and powerplant certificates. He has more than 3,200 flight hours.
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