The need to use this procedure would result from 2 possible worst-case scenarios. As such this procedure should be studied and practiced to maximize your confidence and success in the unlikely event you find yourself in such a situation.
The worst of the worst-case scenarios would be an electrical fire or smoke from an unknown source. It this case your Abnormal/Emergency Checklist would have you with oxygen mask and smoke googles on, battery in the Emer position, likely doing an emergency descent to make it to the airport in less than 30 minutes. Surely a handful for even the best of pilots.
The second worst-case scenario where you would need standby instruments would be if you had an engine failure where the operating engine's generator failed due to the excessive load, all before you were able to get the APU generator on-line. Now you are doing a single engine, standby instrument approach! Not something any of us would look forward to.
Have No Fear! Simply Follow These Steps for The Perfect Standby Instrument Approach:
You have 10 minutes before you must put the battery switch to the Emer position, better to take a minute to set things up right than to rush. Write down the current ATC frequency and advise them of your situation, that you will be going dark and would like an immediate vector to the closest airport. Ident for them and make sure you have their frequency in the #1 Comm. Use the FMS to get your bearings, including terrain. Look over all of the instruments one last time before moving the battery switch to the emergency position.
As soon as practical get the aircraft fully configured for the approach, gear down and landing flaps extended. If you are in a position to do this before you put the battery switch to Emergency with the autopilot engaged even better.
Keep Power Changes to a Minimum:
Once you begin to descend on the approach reduce power to what is normally required to fly a 3-degree glide slope, say 50%. Your speed may be a little fast at first but the power and the speed will continue to slightly decrease as you near the ground.
Pitch to Follow the Glide Slope Using the Manual Trim Wheel:
Accept variations in airspeed to avoid chasing the glide slope. Keep your throttle hand on the trim wheel to resist the temptation to throttle jockey. The proper attitude should be about 2.5 degrees below the horizon as shown in the photo.
CRM is Crucial:
There may be no other procedure that requires greater crew coordination for a successful outcome. The pilot not flying must handle ATC and passenger communications, all while keeping the pilot flying fully advised on height above minimums, outside visual references, speed, localizer and glide slope deviations. The pilot not flying may also be required to adjust power settings.
- Corrections made inside the final approach fix must be very small. You may even want to make course corrections with the rudder to prevent over controlling.
- Use JeppFD or ForeFlight maps on your iPad for situational awareness.
- Request ATC call out distances from the airport at mile intervals.
- If an electrical fire or smoke is NOT the reason you are on standby instruments.
- Consider returning the battery switch to normal after touchdown if runway limited to allow for TR’s and normal braking.
- If you see an abnormally high ITT you may consider tuning the batter switch ON to check if the fire warning is illuminate and then for fire extinguishing capabilities. The battery switch should go back to Emer once the fire has been extinguished.
There you have it, proven techniques to help you master the standby instrument approach. Give it a try next time you are in the simulator and if it goes well try it again, this time single engine! Wouldn’t it be great to have the confidence you can handle it if it ever happened?