Operational Limitations

that you wouldn’t want them extended if a go-around became necessary. (Surprisingly, many speed-brake systems do not auto-retract when go-around [GA] thrust is applied.) Secondly, most operators require that flight crews establish a stabilized landing approach by 1,000 feet AGL, meaning the aircraft is properly configured for landing, “on-speed” (VREF to VREF +10), and descending at a vertical speed of 500–1,000 fpm making speed-brake use unnecessary. In other words, if you still feel the need to use speed brakes below 1,000 feet, you’re probably outside normal approach parameters and would likely be wise to discontinue the approach and execute a go-around or missed approach.

Aircraft autopilot systems have specific limitations that vary widely among manufacturers and aircraft operators. However, there are a few autopilot limitations common to all aircraft that you should be aware of. For instance, since most autopilot systems counter aileron trim inputs and there’s danger of excessive roll when the autopilot is subsequently disconnected, the use of aileron trim with autopilot engaged is commonly prohibited. Another common autopilot limitation covers how soon after take-off autopilot use is authorized. (Restrictions of 200 feet, 500 feet, or 1,000 feet above ground are common.) Autopilot use on approach is also limited to certain altitudes, depending on the type of approach you’re flying and how many autopilots are available as backup. (Many aircraft have two or three autopilots installed.) Additionally, autopilots with auto-land capability have more restrictive maximum crosswind, tailwind, and headwind limits than the limitations of the aircraft itself. Also, most aircraft are only authorized to auto-land with landing flaps extended; auto-landing with any other flap setting is prohibited. The autopilot limitations specific to your aircraft will be covered in ground school and must be committed to memory.

Fuel systems and fuel management procedures also have numerous aircraft-specific limitations. Common to all fuel systems are maximum and minimum fuel temperature limitations. Also, all turbine aircraft have maximum allowable fuel imbalance between wing tanks, and may have different limits for takeoff and landing. Fuel management limitations also define which tanks may be used for takeoff or landing (e.g., takeoff with the center tank supplying the engines is prohibited).

Aircraft maximum operating altitude is the maximum altitude up to which flight operation is allowed, as limited by structural, powerplant, pressurization, load limits, or equipment characteristics. Maximum operating altitude is also dictated by safe operating speed margins between stall speed and high-speed buffets as functions of altitude, angle of bank, and aircraft gross weight. (See Chapter 15, Aerodynamics of High-Speed/High Altitude Aircraft, for further explanation.)

Some aircraft systems may have maximum altitude limitations for operation that are lower than the aircraft maximum operating altitude.

Maximum flap operation altitude is the maximum altitude that an aircraft may be flown with flaps extended, or while flaps are being extended or retracted. Flight above this altitude requires a clean wing; no flaps or slats may be extended.

Maximum Altitude for Auxiliary Power Unit (APU) operations. Most auxiliary power units have maximum altitude operating limitations that are lower than the aircraft’s maximum operating altitude. Some APU’s feature additional altitude restrictions such as maximum altitude for APU start, maximum altitude for APU pneumatic use, or maximum altitude for APU electrical use.

There are numerous limitations you will be required to be familiar with which are operational in nature, rather than relating to aircraft systems per se. Your company operations and flight manuals will thoroughly address such limitations. Let’s take a look at some of the major operational limitations with which you will need to be familiar.

Minimum flight crew is the number of crewmembers considered sufficient by the FAA to safely operate the aircraft considering each individual flight station’s workload, accessibility, and ease of operation of necessary controls. This required minimum flight crew number may change depending on the nature of the flight operation.

The FAA also defines a minimum number of flight attendants required on board the aircraft during each leg carrying passengers. Aircraft seating less than 20 passengers are not required to carry flight attendants. For seating configurations of 20 or more passengers, the minimum number of flight

attendants is one per every unit (or part of a unit) of 50 passengers. For example, a 50 passenger RJ is required to carry one flight attendant, while a 70-seater requires two flight attendants. This minimum number of flight attendants limitation can become confusing during intermediate stopovers where passengers remain onboard the aircraft. Your company’s operations manuals will prescribe your particular aircraft’s minimum flight attendant staffing level for various operational situations.

Pilot Pairing Restrictions are FAA- or companymandated minimum-time-in-aircraft-type limitations, designed to prevent an inexperienced captain from being paired with a brand-new first officer. Currently, the FAA requires a captain or first officer to have at least 75 hours of line operating experience in those positions, in a given aircraft type. Many companies further restrict pilot pairings by not allowing captains and first officers to be paired together unless each has at least 100 hours in position on that type of aircraft. An obvious exception to this rule is pilot pairings on aircraft that are new to the company.

Over age 60 pilot limitations are crew-complement limits placed on pilots who are over the age of 60. A pilot who is over age 60 acting as pilot in command (PIC) in international operations must be paired with a pilot under age 60. (This aligns the U.S. with ICAO requirements.) For domestic operations there is no such crew pairing limitation; both pilots may be over age 60. The FAA further recommends that for flight crews of more than two pilots (such as those required on long international routes) at least one pilot under the age of 60 be at the controls during critical phases of flight, such as take-off and landing.

High-minimums captains are those who have not yet completed at least 100 flight hours as pilot in command in the type of aircraft they are assigned to fly. “High-mins captains,” as the name implies, must conform to higher take-off and landing weather minimums than those with more experience in type.

Virtually all companies provide minimum brake release fuel or minimum fuel for takeoff limitations directly on each flight plan, for pilots to reference prior to each departure. Minimum brake release fuel or minimum fuel for takeoff is the minimum amount of fuel you must carry onboard prior to advancing the thrust levers for takeoff. Most companies also publish aircraft-specific minimum landing fuel and emergency landing fuel levels that must be planned for touchdown. If manual calculations or your FMC indicate you’ll be below those predetermined fuel levels upon landing at your destination, you must request diversion to an alternate airfield if available, notify ATC of your minimum fuel status, or declare an emergency.