Forget Best Glide

In light of the recent accidents, I thought it prudent to discuss engine failures.  This article will not discuss the recent accidents, nor will it attempt to Monday-morning quarterback what could or should have been done differently.  The pilots did exceptionally well in both cases, enough said.  Instead, I want to take a look at some of the hooey that continues to be taught when it comes to engine-out procedures.  This article may very well save your life someday.  Worst case scenario, you’ll have something to read in the bathroom. 

You experience an engine failure what is the first thing you do?  I would be willing to bet that nearly 90% of you say “pitch for best glide.”  You’d be wrong.  “But Shane, the POH says…”  Don’t misunderstand me, I’m not saying that you shouldn’t follow the POH.  What I am saying is that in many cases, the POH does not provide a checklist for the exact scenario you may be faced with.

Defining Best Glide
First of all, we should define what exactly is Best Glide (Vg)?  Is it the speed that will give you more airtime or the speed that will give you the most distance for altitude loss?  Is the Vg listed in the POH valid for all weights?  Don’t know the answers to these questions?  Trust me, you’re in good company.   Best Glide is defined as the speed (at Gross Weight) that will give you the furthest DISTANCE for each unit of ALTITUDE LOST.  That speed will DECREASE as you go below Gross Weight.  An important speed to know, right?  Maybe.  I’m sure many of you know Vx and Vy in your airplanes right?  If not, open the POH right now and find out.  When I do checkouts, I want you to know Vx and Vy cold.  Vg, I don’t care all that much initially.  But isn’t that irresponsible?  Yes, but my mother always said I was that anyway.  The reality is that Vg is roughly halfway between the two.  Let’s take our trusty 172 for instance.  Vx is 59 and Vy is 73.  Take the average of those two and you end up with 66 right?  Vg in the POH is listed as 65.  Is that 1 kt going to mean the difference between life and death; not likely.  So you want to stay in the air longer you say?  OK, no problem, pitch for minimum sink speed.  WHOA, minimum what?  Yeah, that’s a number you will likely not get in your POH (Instructors, listen up).  Funny thing is, the ACS for Private Pilot specifically mentions both of these speeds.  I guarantee you that the majority of the time, minimum sink speed is not even mentioned in a Private Pilot Syllabus.  The next time you want to fly with your instructor, have them help you calculate your Minimum Sink Speed.  First off, it will ALWAYS be slower than your Best Glide speed.  Now that you have that acorn of knowledge, you have a baseline.  Remember the power-required curve?  It is the point at the bottom of that curve.  You want to get the airplane to the FASTEST speed that will produce the SLOWEST vertical speed.

So what if:

  • You are 600′ AGL, in your crosswind turn working in the pattern and lose your engine.  Can you make it back to the runway?
  • You are 7,000′ AGL with an airport 5 miles away.  Can you make the airport?
  • You are over the coast at 500′ AGL.  Will you head toward the shoreline?
  • You are on a straight-in approach, 5 mi out and 3,000′ AFE (Above Field Elevation).  Do you keep going?

First of all, I will provide the disclaimer that you should not practice any engine out procedures without your instructor in the right seat and only if he/she is comfortable performing the maneuvers.  

The Problem
When performing your “Emergency Approach and Landing (Simulated)” during your Private Pilot check ride (or pretty-much any other check ride you do), the ACS says nothing about actually landing.  When we teach this maneuver, most of the time we recover at a safe altitude, debrief and do it all again.  Of course, this is the prudent thing to do when we practice over populated areas where we have to balance training, FAR’s and keeping the peace among the mere mortals on the ground.  In doing these maneuvers with this tunnel-vision though, we are really performing a disservice to all ourselves.  

When working on your Commercial certificate, one of the procedures is a power-off 180 accuracy approach and landing.  The simulation is that if you lose the engine somewhere on downwind, you can safely make it back to the runway and touchdown at a specified point.  The ACS defines this maneuver and the standards but nowhere does it say to “pitch for Vg.”  To paraphase what you should be doing, “you lost your engine on the downwind, land at that spot there, don’t break the airplane or yourself and, oh yeah, take these 100 factors into consideration as you try to make the runway, troubleshoot, make radio calls and order an Uber for your ride home.”  Inevitably though, one of the first things I see pilots do is to pitch for best glide?  Why?  One of the first problems that comes to mind is the majority of the pattern work being done rarely actually resembles a pattern, unless you’re a 747.  I see many pilots well outside of the 1/2 -1 mi pattern that the Airplane Flying Handbook states.  If you lose your engine at any point from Crosswind to Final, there should be no question about making the runway.  If there is, fly a closer pattern.  If you fly one of those cross-country patterns, you neeed Vg just to get back to the airport area.

The Practice
With nearly all of my clients (Private through CFI), I set aside time to perform real emergency procedures in a controlled environment.  How many of you have performed a simulated engine failure to a landing?  How many of you have had your engine [simulated] fail on the upwind?  or crosswind?  It rarely happens in normal training.  I can’t count the number of times I’ve taken a pilot out to practice these maneuvers and at 6,000’+ above a paved runway, killed the engine and NEVER MADE IT TO THE RUNWAY.  This happens with Private Pilots, Commercial Pilots and CFI’s.  Why?  My working theory is that mostly because they never practice.  Additionally, when we practice, we’re doing it wrong.  Remember that takeoff briefing that you do every time before departure when you tell your passengers (and yourself) what will happen if you lose the engine.  Everyone [that performs] the briefing, gets it right.  Land straight ahead when I’m too low, try to make it back to the field when I’m at a safe altitude.  Why then, do nearly 60% of the pilots I have flown with attempt a turn back to the runway after a [simulated] engine failure after takeoff.  Lack of practice?  Perhaps.  Instinct, more likely.  We all hear about and discuss the “impossible turn” early in our aviation careers.  But how many actually practice it.  How much altitude does your airplane lose trying to make it back to the runway.  Once you’ve figured that out, it should stick in your head.  In the Cirrus for instance, you need nearly 1,000’ to safely make that 180 + 45 – 45 Turn (Course reversal, aim at the runway, line up with the runway).  You need to be well above 500’ to even consider a return to the field.  This accident proves that.  Vg in the Cirrus is 88kts.  Immediately after takeoff, you are barely at 90kts.  If you lose the engine immediately after takeoff, you’ll first lose airspeed, then altitude as you push the nose forward to regain speed.  By that time, you’ve likely already lost 100-200’ while trying to process that fact that the airplane now belongs to the insurance company.  In the Cirrus, the decision is relatively easy.  Pull the chute.  We don’t have that luxury in most trainers.  While the 172 may glide halfway to Monterey after losing the engine on takeoff, many of the larger, heavier airplanes have the opposite problem.  Take the Arrow.  I get better gliding distance in my Jeep.  The airplane just doesn’t appear to glide well.  But is that really the case?  The POH for the PA28R says that at 3,000 AGL, you’ll glide approximately 5NM using a Vg of 79KTS.  Have you tried it?  Many things have to happen immediately and succinctly to get book distances from our airplanes.  So how do you know what yours is without trying it?

As an alternative approach to attempting a forced landing in an area with little or no options, I teach a form of a maneuver that many instructors may already know.  With this modified form of the falling leaf, I will have the pilot get the airplane as close to stall as possible without actually stalling.  In the Cessna 206 for instance, I’ve seen the airspeed as low as 35kts.  This configuration includes flaps full, similar to a power off stall.  The airplane is moving FORWARD at ~40MPH.  With the same configuration, we are descending at approximately 700 FPM.  Yikes, hit the ground that fast and you’re surely a goner.  Not so much.  Let’s do some more math.  700 FPM is approx 7 MPH.  If we assume that in general, humans can easily survive a fall at up to 12m/s unprotected, we do a quick conversion and find that 7 MPH is roughly 4 m/s.  Seems like that is a manageable speed to hit the ground, no?  I think with most of my landings I hit the ground that fast. 

So why are we so hung up on flying like robots when the perverbial crap hits that big fan in front of the airplane?  The Law of Primacy comes to mind.  This theory states that the first thing you learn has the greatest effect on your subsequent actions.  It comes down to this.  When we are teaching (and learning) simulated engine failures in flight, we practice them until we have the instinct engrained in our heads.  Pitch for Vg, Find the best landing location, run the checklist, communicate your problems, go onto Facebook and tell your friends what’s happening (I think this is part of the next ACS revision).  We never get to practice or even discuss all of the what if’s.  Call your instructor and tell them you want to go practice emergencies.  We’re lonely anyway and we want to help.

The Solution
Bob Hoover once said, “fly the airplane as far into the crash as possible.”  But what does that mean?  My opinion is, THINK OUTSIDE THE BOX!!!  If you lose your engine at altitude in the pattern, head to the runway, configure as needed, and get the plane on the ground just like a normal landing.  Lost the engine thousands of feet up and near an airport?  Pitch for Vg, head toward that key position (you know what that is right?) of your landing spot and fly a normal pattern.  Lost the engine after takeoff?  Follow your takeoff briefing and land straight ahead.  Maybe you add some of the above advice into your pre-crash checklist.  Bottom line, DON’T EVER STOP FLYING THE PLANE.  Stop acting like a robot and think about your next move.  Think about it when you are sitting on your couch; Think about it when you are headed to the airport.  If you ever have to think about it as it happens though, don’t take too long you’re going to hit the ground soon.  The goal is to do it in a controlled fashion.

Fly, practice, survive.   

You may also like...

Aviation General
System Administrator

Forget the Checklist Already!

I recently sat in on the debrief from one of my student’s check rides. The Designated Examiner had overall positive things to say about the check ride, although there was a question of judgement for using me as her instructor.

Read More »

Leave a Comment