3 Things Every Pilot Needs to Know About… Descents!

Maybe it’s because I am constantly assessing risk, but when I see student pilots who make their first solo in 10, 12 even 15 hours, I often wonder if the student is really prepared… The physical muscle memory associated with learning to properly fly the traffic pattern and land the aircraft in itself takes many hours, more then 10 in my opinion, but that not what I want to discuss today…

Right before I jump out of the airplane to let a student pilot go solo we make 5 very successful trips around the traffic pattern. Three normal takeoffs and landings, full stop taxi back, just like they will do without me. I employ full stop, taxi back landings because a touch and go does not give the vital taxi time to discuss each individual landing. So while touch and go’s during landing training help to maximize the number of landings, using them prevents the proper attention that should be given to each landing to maximize the value of each to make improvements rather than simply repeat the same mistakes. But I digress… The other two trips of the 5 just before the solo are a go around and a simulated engine out to a full stop landing. Typically we do the simulated engine out first and if it looks really good I have the student go around and make it only 4 trips around before I jump out…

My fear is that those “short time” students are limited to emergency training as it is related to simulated engine out practice in the traffic pattern. Not trouble-shooting electrical system issues, how to deal with the different types of fires, etc…

gliding

An aircraft gliding, handles differently than an aircraft under power, a skilled pilot knows the capabilities (range and rate) of their aircraft without power…

Private pilot training should also include a great deal of time-spent gliding… Yes, gliding. A staple of my first reviews is a simulated engine out from aloft to a full stop landing at an airport below (I plan to explore this more in a follow up post here on ReviewBeforeFlight). I often hear how the pilot has never done that before and every time I am shocked that no instructor ever thought, maybe it’d be a good idea to actually play out the entire simulated engine out aloft scenario. Not just completing the A-B-C checklist and then completing a go-around when it is clear the selected landing field is “made”.

Early in a student’s training it is important to climb up to 7,000 feet, maybe even a little higher and then simulated a glide at best glide speed to impress upon the student the actual capabilities of the aircraft without power, that and the limitations. But best glide speed isn’t the only “emergency” speed. In reality it’s one of three.

  1. Best glide speed

When a pilot thinks of an emergency, a simulated engine out is the classic example. The airplane is flying along; the flight instructor reaches over, pulls the throttle back and announces that the engine has failed… The idea is to prepare for the possibility that someday the reduction in engine noise might not be a result of a flight instructor gently easing the throttle back, but instead because of an actual failure of the engine for one of a number of reasons.

The first time you hear the lack of an engine, even if it is only a little ‘skip’ it makes any pilot much more aware of their state. Understanding how to stay cool when the fan out front stops turning, is vitally important. Best glide speed provides the maximum range over the ground without engine thrust. This speed is the speed to employ when a suitable landing site can’t be found in close proximity. I don’t feel a great need to spend too many words on this speed, because this is the one I’m confident everyone flying an aircraft understands and have engrained in their memory from their initial flight training.

  1. Minimum sink speed

This speed is much less often mentioned, yet is just as important as best glide. Did you see that recent video of the ferry pilot that was forced to ditch in the Pacific Ocean when fuel starvation prevented him from having the ability to complete his flight to Hawaii? I’m not here to debate what led to the ditching, which turned out to be like Apollo 13, a successful failure. In that he lived but the plane was ‘lost’… In any event he needed to get the life raft ready and of course take a quick ‘selfie’ on the way down.

The pilot ended up engaging the Cirrus-standard parachute, but had he been in an aircraft without a parachute he could have pitched for minimum sink instead. Knowing he didn’t have the range to make it to the islands, he transitioned to preparing for the worst. Minimum sink slows an aircraft down below ‘best glide’. While this reduces the range in terms of distance of a gliding aircraft, this speed maximizes the time the aircraft is in the air. This gives the pilot/passengers more time to troubleshoot and potentially solve the problem, or to prepare for the forced off-airport landing.

This speed is something I first learned about from Barry Schiff’s May 2006 Proficient Pilot column in AOPA Pilot magazine. After reading his one-page write up I was immediately sold on the value of this concept and quickly started practicing flying at minimum sink speed. Once I became a flight instructor shortly there after, I made sure that each and every student I trained knew about minimum sink. Further, each of the students could explain the difference between best glide and minimum sink and of course, they could each utilize the speed if they were required to do so.

Minimum sink

Minimum sink is all about maximizing the time you have aloft!

To achieve the minimum sink airspeed, the basic rule of thumb (as outlined by Mr. Schiff many years ago in AOPA Pilot) is to find the difference between the best glide airspeed and the power off stall speed. Take half of the difference and add it back to the stall speed, so you end up exactly in between the best glide speed and the power off stall speed for the aircraft. Remember this is a rule of thumb, you can test (at a proper altitude) it out and find the most effective minimum sink speed for your aircraft… This is the minimum sink airspeed that will provide the most time in the air. If you have never attempted this before, please consult a flight instructor and take a CFI with you when you try it for the first time.

  1. Maximum rate of descent speed

This speed provides the most effective/efficient way to lose altitude, while making a quick transition from descent to landing. In 2012 the FAA added the “Emergency Descent” task to the Private Pilot Practical Test Standard (PTS). The Emergency Descent is the procedure to be used when you need to exit the aircraft ASAP, essentially getting to the ground as quickly as possible.

Some may think, point the nose down and ‘ride the top of the yellow arc’. But this would be inappropriate. Sure you would lose attitude in a hurry but instead of dissipating energy, the pilot would be converting potential energy (altitude) into kinetic energy (airspeed). Meaning the airspeed would have to be burned off before the pilot could put the plane down…

max rate

A maximum rate descent doesn’t have to be “on the edge”, in fact it is very controlled. Simply use your bank angle to increase or decrease your rate of descent while maintaining the maximum flap extended speed with your pitch…

The proper procedure would be to slow to the maximum flap operating speed and deploy full flaps (and landing gear if applicable), roll to 30 to 45 degrees of bank while reducing power which will result in the maximum rate of descent while not exceeding the maximum flap operating speed. Once the altitude has been dissipated, a transition can quickly be made to a landing, as the aircraft will not be plagued with excessive speed.

The emergency descent is something a pilot should be well trained in and that’s exactly why I have included it in all of the flight reviews I have administrated since it was added to the Private Pilot PTS. Again, this is something that any pilot in command should be able to do, including those that are student pilots making their early solo flights, their first as pilot in command.

Each of these speeds is critically important and should be a tool in a pilot’s back pocket.

-Fly Safe, @MTElia1B9

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One thought on “3 Things Every Pilot Needs to Know About… Descents!

  1. Great article! I think that with 15 hoyr solo you still need to have a bunch of luck to not have any emergency, even when flying in the cirquit. And a good training makes the flying even safer!

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