By: Marc Nathanson (Retired Lt. Col USAF, DPE, CFI, CFII, MEI)
Today, televised sports events include the use of the instant replay in which the action is replayed in slow motion . This gives the viewer time to see those actions that would otherwise be missed when seen at full speed. We sit in our easy chairs thinking that it's so easy to see all the mistakes and remarkable moves made by the players, but not so easy to do. Flying an aircraft under instrument meteorological conditions (IMC) is no easy task either requiring max attention to keeping the aircraft upright, on the proper course, and in control.
Using the same philosophy, we, as pilots, have the opportunity to slow things down to make control of our aircraft more manageable. Many times, though, we find it difficult to slow down because our mind and bodies tell us it is more comfortable to be fast. By slowing down and giving us time to think through the maneuver or approach, it can help us stay ahead of the game. We like speed. It makes us feel in control, especially in airplanes. Slowing our aircraft down from cruise to approach speed is like driving our car in a 90 MPH zone then into a 25 MPH zone. It is very difficult to slow down and maintain the posted slower speed. Our mind and body are still thinking-”Go fast.”
It will help you better manage the approach phase of your flight by slowing down prior to the initial portion of the approach. How far out to begin decreasing airspeed depends on the type and speed of the aircraft. A jet needs more time and room as opposed to a Cessna 172 that requires only a couple of miles to slow down to a manageable speed.
I have had instrument pilot applicants configure and slow their aircraft to approach speed well before the final approach fix and, although this does not constitute a failure, I debrief this as being wasteful of fuel that might be needed in case of a divert in real instrument meteorological conditions (IMC). I also mention the importance of slowing down to stay ahead of the approach as a poorly flown approach could lead to a missed approach and more precious fuel used. I advocate slowing down earlier when first learning how to shoot instrument approaches with the goal of learning when to slow down to to conserve fuel. Once proficient, you should be configured by the time you reach the final approach fix (FAF) with the landing gear out and the flaps extended to the approach setting. In light aircraft, such as the Cessna 172, configuring 2 miles before the FAF works nicely. This allows time for you to re-trim the aircraft or allow the autopilot to trim. Remember that the aircraft must be stabile which means that that you must be at approach speed, the aircraft configured for the approach, and vertical speed must not exceed 1,000 feet per minute. Go missed if you are not stabilized.
If you, during an instrument approach feel rushed and behind the aircraft, go ahead and slow down. Under IFR you have a couple of ways of doing this. One is to reduce power and configure with some flaps (as recommended by the Pilot Operating Handbook) which should help stabilize the aircraft and lower the stall speed. Another method is to request "delayed vectors.” Air Traffic Control (ATC, normally Approach Control) will vector you and set you up on the approach again. This gives you more time to gain better control of your aircraft and the situation. I liken this to the instant replay in that you can slow things down and allow time for you to figure things out. Not a bad idea when you are task saturated. This is also a good time to ask the controller what they have planned for you. Will they simply give you a 360 degree turn to re-establish your aircraft on a portion of the approach keeping in mind it may not be the final approach segment, or will they vector you onto your final approach course prior to your FAF?
Practicing flying slow is very important. We like to go fast. Fast equates to better control and keeps us away from the dreaded stall. So, when we need to slow down for the landing we have trouble and use up excess runway during the air-run portion of the flare and stand the chance of committing the cardinal sin of landing on the nose gear. We want to get on the ground because we don't want to go back up into the clouds we just escaped-human nature.
An excellent way to practice slowing your aircraft is to fly instrument patterns. Here is an example of one that has you slow down, speed up, and descend, all the maneuvers normally associated with some instrument approaches. Master this and you will be better at controlling your aircrafts' speed and attitude. Practice without the hood first for better situational awareness, then with the hood. The beauty of flying patterns is that they can be flown most anywhere (that does not conflict with airspace or other aircraft traffic).
Fly with another pilot or instructor who can help clear your airspace and write down power settings that result in desired air speeds for the configuration and put these in a performance matrix. For example, in a Cessna 172SP you will find that 2100RPM will result in about 90KIAS when flown clean (flaps up). Add 10 degrees of flaps and note the airspeed as you maintain level flight. Lower the nose to maintain 90 and see what the rate of descent is and use this as a baseline for the ILS. Hint: to help you maintain the ILS glide path, divide the ground speed by 2 and add a zero. This is the approximate rate of descent that will help you maintain the glide path assuming it is 3 degrees. This rate of descent will change as the ground speed changes. Faster ground speed = faster rate of descent to maintain the glide path angle.
Make a matrix based on this information as well as the amount of up elevator trim required to hold altitude. Then, find the power setting that will result in a 500 foot per minute (FPM) descent which will be close to that required to maintain position on the glide path when executing an ILS. You also want to write down the power setting to maintain a 800-1000FPM descent for the non-precision approach after the final approach fix. Remember that 1,000FPM is the maximum rate of descent allowed to maintain a "Stabilized Approach.” I suggest a matrix of power, pitch, trim settings, and air speeds correlated to the different configurations.
There are situations when a missed approach is in order. There are 2 seats from an airliner that sit in a bar in Asia. The airliner they used to reside in landed long as a result of a problem with the airspeed indicating system. The crew could not decide which airspeed indicator(s) were telling the truth so they guessed using the indicator that displayed the highest airspeed. This resulted in an extremely high airspeed and a long air-run. The First Officer (co-pilot) yelled "Put it down" to the captain who was flying-and he did resulting in a very long landing and departure from the end of the runway. Fortunately, both crew members survived, but the aircraft was a total loss. There is now a revised emergency procedure in the manual for this aircraft that better covers "Airspeed miss-compare.” These pilots were faced with making a decision after a long night of flying a very long distance and landing at an airport that was surrounded by mountainous terrain requiring the approach to be flown absolutely perfectly. If they had known the appropriate configurations and power settings for their approach, it would have been easier for the crew to correctly identify the proper airspeed.
Of course, you must execute the missed approach whenever criteria are not met such as:
Not able to identify the landing environment at your MAP (Missed Approach Point) or DA (Decision Alititude).
Loss of vertical or horizontal navigation.
Not positioned to make a "normal" landing through the use of "normal" maneuvers.
To name a few.