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Chapter 11 - Emergency Operations

Chapter 11 - Emergency Operations


Changing weather conditions, air traffic control (ATC), the aircraft, and the pilot are all variables that make instrument flying an unpredictable and challenging operation. The safety of the flight depends upon the pilot’s ability to manage these variables while maintaining positive aircraft control and adequate situational awareness. This chapter will discuss the recognition and suggested remedies for such abnormal and emergency events related to unforecasted, adverse weather, aircraft system malfunctions, communication/navigation system malfunctions, and loss of situational awareness.

Unforecast Adverse Weather

Inadvertent Thunderstorm Encounter

A pilot should avoid flying through a thunderstorm of any intensity. However, certain conditions may be present that could lead to an inadvertent thunderstorm encounter. For example, flying in areas where thunderstorms are embedded in large cloud masses may make thunderstorm avoidance difficult, even when the aircraft is equipped with thunderstorm detection equipment. Therefore, pilots must be prepared to deal with an inadvertent thunderstorm penetration. At the very least, a thunderstorm encounter will subject the aircraft to turbulence that could be severe. The pilot, as well as the passengers, should tighten seat belts and shoulder harnesses and secure any loose items in the cabin.

Emergency: A distress or urgent condition.

As with any emergency, the first order of business during an inadvertent thunderstorm encounter must be to fly the aircraft. The pilot workload will be high; therefore, increased concentration is necessary to maintain an instrument scan. Once you enter a thunderstorm, it is better to maintain a course straight through the thunderstorm rather than turning around. A straight course will most likely get you out of the hazard in the least amount of time, and turning maneuvers will only increase structural stress on the aircraft.

Reduce power to a setting that will maintain a speed at the recommended turbulence penetration speed as described in the Pilot’s Operating Handbook/Airplane Flight Manual (POH/AFM), and try to minimize additional power adjustments. Concentrate on keeping the aircraft in a level attitude while allowing airspeed and altitude to fluctuate. Similarly, if using the autopilot, disengage the altitude hold and speed hold modes, as they will only increase the aircraft’s maneuvering—thereby increasing structural stress.

During a thunderstorm encounter, the potential for icing also exists. As soon as possible, turn on anti-icing/deicing equipment and carburetor heat, if equipped. Icing can be rapid at any altitude and may lead to power failure and/or loss of airspeed indication.

Lightning will also be present in a thunderstorm and can temporarily blind a pilot. To reduce this risk, turn up cockpit lights to the highest intensity, concentrate on the flight instruments, and resist the urge to look outside.

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Inadvertent Icing Encounter

Because icing is unpredictable in nature, pilots may find themselves in icing conditions even though they have done everything to avoid it. In order to stay alert to this possibility while operating in visible moisture, pilots should monitor the outside air temperature (OAT).

Proper utilization of the anti-icing/deicing equipment is critical to the safety of the flight. If the anti-icing/deicing equipment is used before sufficient ice has accumulated, the equipment may not be able to remove all of the ice accumulation. Refer to the POH/AFM for the proper use of anti-icing/ deicing equipment.

Prior to entering visible moisture with temperatures at 5° above freezing or cooler, activate the appropriate anti-icing/deicing equipment in anticipation of ice accumulation—early ice detection is critical. This may be particularly difficult during night flight. You may need to use a flashlight to check for ice accumulation on the wings. At the first indication of ice accumulation, you must act to get out of the icing conditions.

There are four options for action once ice has begun to accumulate on the aircraft:

  1. Move to an altitude with significantly colder temperatures;
  2. Move to an altitude with temperatures that are above freezing;
  3. Fly to an area clear of visible moisture; or
  4. Change heading and fly to an area of known nonicing conditions.

If none of these options are available, you must consider an immediate landing at the nearest suitable airport. Anti-icing/ deicing equipment is not designed to allow aircraft to operate in icing conditions indefinitely. Anti-icing/deicing equipment will simply give you more time to get out of the icing conditions.

Precipitation Static

Precipitation static, often referred to as P-static, occurs when accumulated static electricity is discharged from the extremities of the aircraft. This discharge has the potential to create problems for the instrument pilot. These problems range from the serious, such as the complete loss of very-high

Precipitation static: A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it.

frequency (VHF) communications and erroneous magnetic compass readings, to the annoyance of high-pitched audio squealing, and St. Elmo’s Fire. [Figure 11-1]

Precipitation static is caused when an aircraft encounters airborne particles during flight (e.g., rain or snow), and develops a negative charge. It can also result from atmospheric electric fields in thunderstorm clouds. When a significant negative voltage level is reached, the aircraft will discharge it, which can create electrical disturbances.

To reduce the problems associated with P-static, the pilot should ensure the aircraft’s static wicks are properly maintained and accounted for. Broken or missing static wicks should be replaced before an instrument flight. [Figure 11-2]

St. Elmo’s Fire: A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.

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Aircraft System Malfunctions

Preventing aircraft system malfunctions that might lead to an inflight emergency begins with a thorough preflight inspection. In addition to those items normally checked prior to a visual flight rule (VFR) flight, pilots intending to fly under instrument flight rules (IFR) should pay particular attention to the alternator belt, antennas, static wicks, anti-icing/deicing equipment, pitot tube, and static ports.

During taxi, verify the operation and accuracy of all flight instruments. In addition, during the runup, verify that the operation of the pneumatic system is within acceptable parameters. It is critical that all systems are determined to be operational before departing into IFR conditions.

Alternator/Generator Failure

Depending upon the aircraft being flown, an alternator failure is indicated in different ways. Some aircraft use an ammeter that indicates the state of charge or discharge of the battery. [Figure 11-3] A positive indication on the ammeter indicates a charge condition; a negative indication reveals a discharge condition. Other aircraft use a loadmeter to indicate the load being carried by the alternator. [Figure 11-4] If the alternator were to fail, then a zero load indication is shown on the loadmeter. Sometimes an indicator light is also installed in the aircraft to alert the pilot to an alternator failure. Review the appropriate POH/AFM for information on the type of systems installed in your aircraft.

Ammeter: An instrument installed in Loadmeter: A type of ammeter series with an electrical load to installed between the generator measure the amount of current output and the main bus in an aircraft flowing through the load. electrical system.

Once an alternator failure has been detected, the pilot must reduce the electrical load on the battery and land as soon as practical. Depending upon the electrical load and condition of the battery, there may be sufficient power available for an hour or more of flight—or for only a matter of minutes. You should also be familiar with what systems on the aircraft are electric and which continue to operate without electrical power. The pilot can attempt to troubleshoot the alternator failure by following the established alternator failure procedure published in the POH/AFM. If the alternator cannot be reset, advise ATC of the situation and inform them of the impending electrical failure.

Instrument Failure

System or instrument failure is usually identified by a warning indicator or an inconsistency between the indications on the attitude indicator and the supporting performance instruments. Aircraft control must be maintained while identifying the failed component(s). Expedite the cross-check and include all the flight instruments. The problem may be individual instrument failure or a system failure that affects several instruments.

One method of identification involves an immediate comparison of the attitude indicator with the rate-of-turn indicator and vertical speed indicator (VSI). Along with providing pitchand-bank information, this technique compares the static system with the suction or pressure system and the electrical system. Identify the failed component(s) and use the remaining functional instruments to maintain aircraft control.


Attempt to restore the inoperative components(s) by checking the appropriate power source, changing to a backup or alternate system, and resetting the instrument if possible. Covering the failed instrument(s) may enhance your ability to maintain aircraft control and navigate the aircraft. Usually the next step is to advise ATC of the problem and, if necessary, declare an emergency before the situation deteriorates beyond your ability to recover.

Pneumatic System Failure

One possible cause of instrument failure is a loss of the suction or pressure source. This pressure or suction is supplied by a vacuum pump mechanically driven off the engine. Occasionally, these pumps fail, leaving the pilot with inoperative attitude and heading indicators. [Figure 11-5] Many small aircraft are not equipped with a warning system for vacuum failure; therefore, the pilot should monitor the system’s vacuum/pressure gauge. This can be a hazardous situation with the potential to lead the unsuspecting pilot into a dangerous unusual attitude—which would require a partial panel recovery. It is important pilots practice instrument flight without reference to the attitude and heading indicators in preparation for such a failure.

Pitot/Static System Failure

A pitot or static system failure can also cause erratic and unreliable instrument indications. When a static system problem occurs, it will affect the airspeed indicator, altimeter, and the VSI. In most aircraft, provisions have been made for the pilot to select an alternate static source. Check the POH/AFM for the location and operation of the alternate static source. In the absence of an alternate static source, in an unpressurized aircraft, the pilot could break the glass on the VSI. The VSI is not required for instrument flight and breaking the glass will provide the altimeter and the airspeed indicator a source of static pressure. This procedure could cause additional instrument errors.

Communication/Navigation System Malfunction

Avionics equipment has become very reliable, and the likelihood of a complete communications failure is remote. However, each IFR flight should be planned and executed in anticipation of a two-way radio failure. At any given point during a flight, the pilot must know exactly what route to fly, what altitude to fly, and when to continue beyond a clearance limit. Title 14 of the Code of Federal Regulations (14 CFR) part 91 describes the procedures to be followed in case of a two-way radio communications failure. If the pilot is operating

Clearance limit: The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance.

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in VFR conditions at the time of the failure, the pilot should continue the flight under VFR and land as soon as practicable. If the failure occurs in IFR conditions, or if VFR conditions cannot be maintained, the pilot must continue the flight:

  1. Along the route assigned in the last ATC clearance received;
  2. If being radar vectored, by the direct route from the point of radio failure to the fix, route, or airway specified in the vector clearance;
  3. In the absence of an assigned route, by the route that ATC has advised may be expected in a further clearance; or
  4. In the absence of an assigned route or a route that ATC has advised may be expected in a further clearance, by the route filed in the flight plan.

The pilot should maintain the highest of the following altitudes or flight levels for the route segment being flown:

  1. The altitude or flight level assigned in the last ATC clearance received;
  2. The minimum altitude (converted, if appropriate, to minimum flight level as prescribed in part 91 for IFR operations); or
  3. The altitude or flight level ATC has advised may be expected in a further clearance.

In addition to route and altitude, the pilot must also plan the progress of the flight to leave the clearance limit:

  1. When the clearance limit is a fix from which an approach begins, commence descent or descent and approach as close as possible to the expect-further-clearance time if one has been received; or if one has not been received, as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time en route.
  2. If the clearance limit is not a fix from which an approach begins, leave the clearance limit at the expect-furtherclearance time if one has been received; or if none has been received, upon arrival over the clearance limit, and proceed to a fix from which an approach begins and commence descent or descent and approach as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time en route.

While following these procedures, set the transponder to code 7600 and use all means possible to re-establish two-way radio communication with ATC. This includes monitoring navigational aids (NAVAIDs), attempting radio contact with other aircraft, and attempting contact with a nearby automated flight service station (AFSS).

Loss of Situational Awareness (SA)

Situational awareness (SA) is not simply a mental picture of where you are; rather, it is an overall assessment of each element of the environment and how it will affect your flight. On one end of the SA spectrum is a pilot who is knowledgeable of every aspect of the flight; consequently, this pilot’s decision making is proactive. With good SA, this pilot is able to make decisions well ahead of time and evaluate several different options. On the other end of the SA spectrum is a pilot who is missing important pieces of the puzzle: “I knew exactly where I was when I ran out of fuel.” Consequently, this pilot’s decision making is reactive. With poor SA, this pilot lacks a vision of future events and is forced to make decisions quickly, often with limited options.

During a typical IFR flight, a pilot will operate at varying levels of SA. For example, a pilot may be cruising to his/her destination with a high level of SA when ATC issues an unexpected standard terminal arrival route (STAR). Since the pilot was not expecting the STAR and is not familiar with it, SA is lowered. However, after becoming familiar with the STAR and resuming normal navigation, the pilot returns to a higher level of SA.

Factors that reduce SA include: distractions, unusual or unexpected events, complacency, high workload, unfamiliar situations, and inoperative equipment. In some situations, a loss of SA may be beyond a pilot’s control. For example, with a pneumatic system failure and associated loss of the attitude and heading indicators, a pilot may find his/her aircraft in an unusual attitude. In this situation, established procedures must be used to regain SA.

As a pilot, you should be alert to a loss of SA any time you find yourself in a reactive mindset. To regain SA, you must re-assess your situation and work toward understanding. This may mean you need to seek additional information from other sources, such as the navigation instruments or ATC.