Preparatory Ground Instruction for Forced Approaches
- Preparatory Ground Instruction for Forced Approaches
A forced approach is a condition in which a landing is mandatory owing to a full loss of power, a partial loss of power, or an engine fire.
The student will learn a systematic and effective procedure for managing a forced approach condition, including field selection, execution are vital action emergency checklists, and conducting a successful approach and landing on an unprepared surface.
The ability to conduct a successful forced approach in response to in-flight emergencies is perhaps one of the most important skills the pilot has.
Causes of Forced Approaches
The background knowledge of this PGI should begin with a review of some of the causes of the forced approaches. A list should be written up on the whiteboard, drawing on the student knowledge, and as the items are presented, the instructor should provide some background information related to the individual causes—fuel exhaustion, for example, is easy to understand as a cause for engine failure because it is an essential component in the internal combustion process, buy why to pilots sometimes fail to have enough fuel on board? When the list is exhausted, the instructor should review the list a second time with the student, addressing this time whether or not pilot actions in response to the cause might provide a remedy—e.g., switching fuel tanks, turning on the backup electric fuel pump, applying carb heat, etc. Clearly, the pilot response in completing vital action is critical. Some causes, such as the catastrophic failure of an aircraft engine, or an engine fire, cannot be remedied, but a review of this list with respect to the effect of pilot response will point out to your student that the vital actions and checklist performed by the pilot after an in-flight emergency is encountered are crucial.
To be successful at forced approaches, students must have a realistic idea of the gliding capabilities of the aircraft. This is accomplished by reviewing the performance data presented in the Pilot Operating Handbook with respect to gliding distances, but students should also be provided with an accurate means of visualizing the glide radius from the aircraft during flight. Generally speaking, a glide radius passes just below the nose of the cowling, and through two points on either side of the aircraft, just below the wing tips. In the case of Cessna aircraft, the radius can be mapped out using the wing struts as reference. It should be emphasized for students that landing areas near the limits of the glide radius should be avoided, as pre-landing maneuvering of the aircraft here becomes more and more limited as the aircraft approaches the glide limit near the ground (only a straight in approach will work as the limit of the glide radius is approached).
Take time to review with the student the point-of-zero-movement recognition—a skills critical to evaluate the success of forced approaches. Point out the apparent movement of the training above and below the point of zero movement, with terrain appearing to move upward and downward, respectively, in the windscreen.
Pilot Operating Handbook Requirements
Review with your student the checklists for engine failure and fire. Hopefully, you will have assigned these as homework after the student's previous lesson.
The how section should focus on constructing the correct action response sequence to an engine failure or fire, and this should be created jointly with the student and listed on the whiteboard. When the student derives the next correct action response through joint discussions with the instructor, the instructor this provides more detailed information related to the action.
Note that two action-sequence flows should be created, the first being the pilot response to an engine failure, and the second being the pilot response to engine fire. It is generally more convenient to proceed with engine failure first, where all the initial details are reviewed sequentially, and when this is complete, move on to variations and considerations related to the engine-fire response. Additionally, it is good practice is to breakdown the long string of actions into smaller sections, each with a logical purpose—this makes it easier for the student to organize the memory items.
Under this heading, your list begins with aircraft control, including trimming the aircraft for its maximum distance glide speed, and selecting carb heat on. It is important to emphasis to the student the critical importance of properly trimming the aircraft for the correct speed. If this is done correctly at the beginning of the descent, the aircraft will behave itself during subsequent maneuvering, maintaining the correct speed like an autopilot, provided of course the student doesn’t push or pull on the control column on the way down
Included as part of the immediate response is field selection, and it must be pointed out to students that they must consider landing site options on both sides of the aircraft—it is common for students to look for landing sites only on their side of the aircraft, neglecting the fact that half of the landing site options are on the passenger’s side of the aircraft.
Field selection is one of the most important decisions made by pilots during a forced approach. No matter how effective they are at completing checklist items, and no matter how accurately they fly their approach pattern, a poor landing site selection, even on an open field, can have catastrophic effect. It is therefore appropriate at this time in your PGI to review field selection. Some instructors elect to discuss the subject of field selection in the background knowledge section of the PGI so that it doesn’t detract from the flow in the how section; others just make it an element of how.
Keep field selection focused, and point out the color variations in fields. Point out that there are green fields and brown fields, and that the green fields are generally more favorable as landing sites than the brown fields, but that caution has to be used in both cases.
A green field could be a perfect choice, such as hayfield are sod farm, but a green fuel could also be a long standing crop—for example, a cornfield with nine-foot plants. Point out that the difference between the two is not always readily apparent from altitude, but that clues to the presence of a standing crop can be found by carefully examining the outside boundary of the crop, where a cross-section, and therefore the height of the plants might be visible, especially if the sun is casting shadows.
There are two variations that are common with respect to brown fields; they could be plowed fields, which of course would immediately overturn an aircraft attempting to land, or they could be freshly harvested fields, in which the crop was removed with heavy machinery, making it more suitable for landing. Harvested fields can sometimes be identified by a standing stubble, remaining on the field after the crops have been removed. This will give the appearance of a light brown color. Plowed fields are uniformly brown, with no apparent stubble, but they too can be a light brown in color, or dark brown in color, depending on how long the field has lay fallow. Brown fields must certainly approached with caution because of the risk of the aircraft overturning, and all the unfortunate consequences that come with it.
A final variation on fields is pasture fields where animals are apparent; these field surfaces are generally uneven, and can be undulating, but provide relatively firm surface for touchdown.
You should also discuss with your student the option of landing on road surfaces, but these present their own series of hazards. Wires typically cross a road surface where the road is adjacent to a building, house, or other structure, as electrical power is typically required. There is the risk of encountering road traffic, and road services are generally narrow, making them hazardous in crosswind situations. Nevertheless, roads may be the only option, especially when flying in a mountainous area. In non-populous area where there is agricultural activity, they are clearly the best choices.
Plan the Approach
Once the field is selected, the pilot should quickly formulate a plan for the approach pattern. There are many variations in preferences here, but I think the primary obligation on the instructor here is to convey to the student the variety of approach patterns that are conventionally used. Begin with your preferred approach pattern and then discuss alternates. Generally, the approach patterns used by pilots can be divided into the circuit pattern, the circling pattern, and the bowtie pattern. With each of these, you should discuss the advantages and disadvantages. Whatever the pattern used, discuss the importance of targeting the center of the field initially, and only when the landing is assured at the center, should flaps and slips be used as required to move the touchdown point towards the approach end of the field.
With respect to disadvantages, the circuit pattern provides a lack of consistency with respect to the rate of closure on the landing target—sometimes the aircraft is moving parallel to the selected field (as is the case in the downwind leg, abeam the field), sometimes the aircraft is moving away from the selected field (as is the case in late downwind), and sometimes it is moving toward the selected field (base and final legs). These varied rates of closure, relative to the touchdown target, make it difficult for the brain to evaluate glide success. The same difficulty in evaluating client success is experienced in the bowtie approach, and perhaps still more extreme level. Maintaining a constant distance from the target field during the bowtie approach requires extreme turns towards and away from the landing area, making assessment of the glide path difficult—again, it is difficult for the brain to assess rate of closure on the touchdown target.
With respect to the advantages, the circling approach perhaps leads the pack, as the closure rate to the touchdown target remains constant during the circling maneuver. Moreover, the constant, sustained angle of bank means the generation of lift remains constant. Finally, if the aircraft is other that the Cessna 172-type production series, the pilot is afforded good visibility of landing area (this is not the case, of course, if the pilot is required to circle to the right during the approach). The advantage of the circuit approach pattern is that pilots are familiar with its design and characteristics, and of course for most Cessna aircraft, the touchdown target can be seen. The advantage of the bowtie approach is that it keeps the aircraft nicely placed on the baseline during the final phases of the approach.
With respect to the final phases of forced approach, explain to your student the importance of utilizing all drag tools that are available so that the glide path can be controlled effectively. Landing flap should not be selected until touchdown is assured, and flaps—overall—should be used cautiously as a reverse decision to retract the flaps will have the cost of losing lift; in contrast, the use of slipping as a means losing altitude can easily be discontinued by the pilot without a lift-loss penalty.
Restart or Cause Check
After the immediate response by the pilot, including the selection of the field, the next phase in the forced approach is the restart. Students should be taught to do a systematic sweep of the cockpit, resembling the pre-landing checks, which of course the student is familiar with—this can be executed quickly as an automatic, learned sequence of actions. The problem with the pre-landing checks are that they don’t address variable settings for such items as magneto selection, varied throttle settings, and varied mixture settings—these are all critical to the efforts to remedy the situation, and should be added on to the end cause check phase of the descent.
Where time permits, the cause checks should include an active review of the emergency checklist—just in case something was missed in the heat of the moment. It is assumed, nevertheless, that emergency vital actions where rapid response are required are memorized by the pilot.
The no start phase has to sub phases: communication and shutdown. The ELT should be activated when possible. Students should be taught the standard distressed communication required, including decision-making with respect to the frequency used, and students should also be taught how to sweep the cockpit for rapid shutdown of fuel and electrics. The final step in the no start phase is the briefing of passengers regarding the stowage of baggage, the removal of sharp objects from pockets, and the tightening of seat belts.
Recovery and Overshoot
This is a critical add-on item for forced approach PGIs, as the overshoot from an altitude just above the ground, and from a position over an improvised landing area, has great risk, especially as it relates to flap retraction and lift management. Be sure your student has a clear understanding of the words you will use to command the discontinuation of the exercise—“recover”, or “overshoot”, are common expressions. Be sure your student is aware of the correct sequence required to execute flap retraction during an overshoot. The power must be applied smoothly so as not to produce engine stutter, and as the nose of the aircraft is smoothly placed into the climb attitude, the flap retraction should be immediately but smoothly accomplished from landing flap to takeoff flap. The carb heat should be selected off, and when obstacles no longer present a threat, the takeoff flap positions should be cleared to a zero-flap setting.
Because the timing is critical here, and there is little margin of error, instructor must to a final visual sweep to ensure the student hasn’t actually shut off the fuel during the simulation.
Variations for Engine Fire
Return now to review the forced approach sequence in the case of an engine fire. Obviously the pilot's engine fire response vital action sequence has to be immediately executed, and equally obvious, the pilot doesn't attempt to restart the engine. The engine fire check list is a critical backup to the remembered vital actions, and this is the next priority once the landing area has been selected. Landing area selection cannot be deferred, as an engine failure or fire could occur at low altitude where viable options for landings are drastically reduced.
Review the collision risks associated with practicing forced approaches. Training cruise in the practice area tend to congregate in the vicinity of favored fields, especially in the lower Fraser Valley region. A simulated engine failure or fire should never be initiated without an effective check for traffic in the vicinity, and especially below the aircraft. As well, the pre-initiation of the maneuver should include an effective radio broadcast that includes accurate position reporting. Included is a vital action in forced approach practice is the turning on of the carb heat, and the selection of electronic fuel pump in the on position. Review also your requirements for periodic engine throttle-up/warm-up (it is not recommended to enforce an “every 500’ rule” or something like that as this distracts from the action that is occurring outside the windscreen—how about a warmup after the cause checks, and after the shut-down). Review the altitude limits which govern forced approach practice, emphasizing that students are initially restricted to not descending below 500’ AGL in solo forced approach practice. Review also the minimum altitude rules for low flying. Review again the overshoot procedure, which is perhaps the highest risk sequence during forced approach practices, and remind your student to keep a good lookout for traffic during the subsequent climb away from the landing area.
See if your student can recall the sequences. As about the field choices. The remaining questions should emphasize safety