[For full details of the techniques used refer to: Practical Flying Guide 1 - Visual Navigation.]
This lesson will require some careful consideration and planning by the instructor to ensure the sequence of lesson objectives flows smoothly and does not become overly complex.
Impress upon the student that an inadvertent entry into IMC is a genuine emergency, and that the procedures you will teach need to be well learnt, so that they can be recalled when under stress. Discuss the actions to take to avoid flying inadvertently into IMC, and the actions to take if this happens, emphasising that the main priorities are to decisively establish an instrument scan, keeping the aircraft safe whilst planning a return to VMC.
Brief the procedures for when uncertain of position using TIME-MAP-GROUND, and the procedures when lost. Emphasise the importance of keeping track of heading and time, and not ‘wandering around’. Explain the initial actions focus on getting some help, and that the secondary actions follow when help is not available, and a plan of action is needed to locate the aircraft’s position.
Lookout. Assessment of weather.
Regular cruise checks, alignment of DI, and descent checks for low level.
Decision making to avoid inadvertent IMC using “Minimum VFR Altitude to Continue”, and “Minimum Safe Altitude” calculated during planning.
The student can carry out all the necessary actions and procedures to get airborne and set off on track at normal operating altitude on the first leg of the planned route.
At a suitable point take control and ask the student to put on a ‘hood’ and simulate a deterioration in weather and an inadvertent entry into IMC. Demonstrate the first action of maintaining control by decisively transferring from visual references to the instruments, building a scan whilst straight and level, and ensuring the aircraft is in trim. Then review MSA and either climb to MSA if the aircraft is below this altitude or descend to MSA if above. In most cases a return to VMC can be achieved by a 180⁰ turn. Whilst this may not always be the case, there is a risk of making the scenario too complex, and the desired learning may not take place. Therefore, keep the exit strategy simple and teach the 180⁰ turn. This should be planned with a target heading. Point out that once the turn is complete, some time may pass flying straight and level before exiting IMC. Also discuss actions in case this does not work. Maintaining the instrument scan, squawking 7700 and transmitting a “Distress” call to ATC without delay. During the debrief, discuss other potential scenarios of the recovery from IMC as discussed in the Visual Navigation guide.
Once you have completed the demonstration, place the aircraft in a suitable position and altitude, and give the student control so that they can practice these procedures.
Once the student has completed the recovery from IMC, take control and ask them to remove the ‘hood’. Point out and fly overhead a feature on the ground, taking up a new heading, and noting the time. Then ask the student to put the ‘hood’ back on, hand control back to them and instruct them to maintain straight and level flight, on the new heading. Ask them to carry out a cruise check, and to update the fuel plan, or other similar tasks. This will be good instrument flying practice but will also keep them slightly distracted from the aircraft position. Whilst maintaining the heading, take control, and whilst the student is under the ‘hood’ ask them to locate the aircraft’s position on the map. Ideally, they will use TIME-MAP-GROUND, and based on the heading flown and time elapsed since flying overhead the feature, they will be able to approximate position on the chart.
Hand control back to the student, and whilst maintaining the heading, ask them to descend to low level. After a few minutes, take back control, ask the student to remove the ‘hood’ and teach the ‘lost’ procedure.
The instructor needs to emphasise the priorities if the student becomes lost. Safety of the aeroplane is of prime importance. Noting down the time, remaining in VMC, maintaining an effective lookout and carrying out a cruise check (particularly DI to compass check and fuel endurance remaining) should be the first actions. Point out the risk of “wandering” off the heading, and that the heading should be maintained. Then make a call to the most appropriate ATC unit, most likely FISCOM, declaring being lost and requesting assistance. If this is unsuccessful, maintain the heading until a visual feature is seen. Then hold overhead that feature, noting down the time, and trying to identify it using GROUND – MAP.
Ask the student to check the actual heading flown since the last confirmed fix, and the time taken from that fix to the current position. From the last fix, they can plot the track flown, and add 6-Minute Markers to establish a DR fix and construct a “circle of uncertainty”, radius 10% of the distance flown since the last reliable fix. They should select a line feature on the map outside the circle of uncertainty. Hand control back to the student and they can set heading towards the line feature, map reading using GROUND - MAP. On reaching the line feature, they should fly along it until another feature is found and the aircraft position is established.
The result of this teaching should give a fix on the chart, from which the student can practise calculating an in-flight diversion to return the aircraft to the home airfield.
4 Inadvertent IMC and lost procedure whiteboard layout [PDF 641 KB]