The Grey Area


Hazel, awaiting engine start

The thing that I struggled with the most when I was training was radio work. I readily admit that to any student pilot, or newly minted private pilot, when I meet them and they ask me what was most difficult. Radio work is the source of one of my more embarrassing mistakes that I still make every few months.

But in a meta-sense, or in the long term, the hardest thing for me about learning to fly (and continuing to learn to fly better) was trying to reconcile all of the different advice I was getting. And the more reading I did (and especially the more reading Adam did), the more we identified things that were Old Wives Tales (OWT on the web boards we were visiting). Since then I have learned that there are lot of topics that you can introduce to a table full of pilots and get an endless discussion (or a short argument where someone leaves in a huff).

So as I meander along my path to becoming The Perfect Pilot, I try to separate the wheat from the chaff. Recently I have begun conversing with Tim Kramer, a pilot with a lot more experience who is an MEII (the FAA even named him the 2010 Michigan Flight Instructor of the Year). Now he’s retired from his regular job in the automobile industry and just teaches Navy graduate students how to fly up in Monterey. He flies the same plane that I flew for ten years, the DA40. When he bumped into my blog and read some (probably too many) of the entries he said that he realized we had landed in a lot of the same airports, flying a lot of the same sort of missions (dragging our small families around the country).


Abel, wistfully watching engine start

When I was learning to fly the Twinstar my instructor said, “Rotate at 80, climb out at 90.” Then during the check ride the Designated Pilot Examiner said, “No no, climb at 105, I like to see over the nose so I know if we’re going to hit something. Close to the airport it is more important to be able to search for traffic.” All climb outs during the check ride were at 105, of course. Then I flew with an aviation mentor who said, “The Vr on the DA42 2.0 is actually 76 knots.” So now I start a sort of gentle pressure at 76 knots and see how it is feeling. Of course, when I went down to Angel City Flyers to tune my landings (great results), the MEII listened to me about the DPE and climb out speed and said, “I’d much rather get some altitude in case I was going to have an engine failure, so I suggest climbing at blue line.”

Tired yet?

The conflicting advice also came into play on landing. Originally I was told to keep it at 90 knots the entire way round and then adjust to “a little slower, probably 80” on short final. During the last landing clinic I was told 78 knots on short final. That’s very specific, and I like that. I easily cut a thousand feet off my landing roll when I hit that number really exactly. But the blue line is still in the forefront of my concern (and faster than 78 knots).


The Banning Pass below

What is blue line?

First, let’s talk about the red line. In a twin-engined airplane a lot of the aeronautical engineering is about what happens to the craft when there is only one engine running. Or, rather, the worse case scenario, which is one engine turning and the other stopped but not yet secured. That’s maximum drag on one side with only one engine available for thrust. You would think the worst thing that could happen is that the plane would twist to one side and motor along through the sky like a duck with a cramped foot. You would be wrong. If there isn’t a big enough rudder to counter the yaw, and if the slow wing gets too slow, then the plane will enter a spin. That sounds so mild compared to what really happens, which is that the plane rolls over toward the failed engine, the good engine wing coming up over high, and the nose then dropping. Apparently it is sudden, ugly, and usually entirely deadly. (“You go upside down, then plummet toward the ground,” was how one Multi-engine Instructor described it. Lovely.)

So we need a minimum airspeed to retain control in situations where we have only one engine turning. (The Twinstar has an advantage because the engines are particularly close to the centerline of the plane, which means a little less adverse yaw. It is also foolishly easy to secure the engine (a single switch, click); there should be a very short time that you have the drag of the windmilling propeller.) That minimum airspeed is the red line, also known as Vmc (Velocity, minimum control). Obviously, it doesn’t really matter if you are flying below the red line, but as a safety measure, if you stay at or above the red line, fewer bad things can happen to you if you lose an engine. (And you have to be faster than red line if you are on one engine.)

Blue line is a little faster, it is the airspeed that yields the best climb rate on a single engine (Vyse). In my head, I don’t want to be slower than even blue line. Red line I would rather never see. I blurred these together so effectively in my mind that in an earlier version of the post I had misnamed the red line as the blue line. The blue line speed in the DA42 is 82 knots. The red line, Vmc, is 68 knots.


Arrival at Palm Springs airport

In some ways my flying has become a lot safer and simpler with the new plane. But it has also gotten a more complicated and there are more options. The plane is certified for Flight Into Known Icing (FIKI), but what does that mean when I am above the clouds and it is 20F outside? Can I start the approach, something I would never do in the Diamondstar? And the plane now carries so much fuel (basically double what the Diamondstar could haul) that I cannot follow my simple rule that I used for my first decade of flying: Never take off unless the tanks are full. And for landing speed and climb out speed, can I drop below the blue line? If I am primed to push the nose down (gain airspeed) on the slightest hiccup in one of the engines, is it okay to be at, or a little below, that blue line?

Part of the temptation is that landing slower means you are a lot less likely to have a problem on landing. The large aviation insurance company, Avemco, tabulated accidents and incidents their clients had and something like 40% were “loss of directional control on landing.” That’s just landing too fast or in conditions that were not good enough to land in. So slower is safer for landing. And when you take off you are trading airspeed for altitude. A slower climb usually means you are gaining altitude at a better clip. Altitude is always your friend in an airplane, the more you have the more options you have if something goes wrong.

This means I am now a pilot who has to consider these contradictions, including often conflicting advice from different instructors, and make my own rules.

Tim’s perspective on this gray area of learning to be a better pilot in his own words:

I too struggled with that early on. For example, was maintaining blue line always preferred or were there times like landing on a short runway when a slower speed would be better. By the time I became an instructor thirty years after I started flying, I realized there were no black or white rules. It took a more balanced look at all of the present risks to decide on the minimal risk approach during that moment. Instructors have different experiences (or they have read different flying stories), so they have different risks dominating their thinking and advice. And the new pilot receiving the advice is another variable. I might tell a low-time twin pilot to always stay faster than blue line but another pilot in a different plane may present fewer risks for single engine controllability or climb capability and in special cases dropping below blue line might minimize other risks. These would be very rare situations. We don’t often get into the secondary discussion of which risks we are mitigating and quantifying those risks in relation with other risks that suggest an opposite course of action.

An example of conflicting advice is the best speed for climb out at takeoff. Should you rotate at minimal rotation speed, initial climb at Vx till you have cleared all obstacles, and then accelerate to Vy best rate until reaching cruise altitude? Well, maybe. But because most of us are flying out of longer, paved, public airports the preferred best alternative is usually slightly faster with a more shallow climb. Rotate at Vx when climb is assured, accelerate in ground effect most quickly to Vy where you have better stall margins in case there is a sudden gust or unexpected wingtip vortex encounter, and climb at a higher cruise-climb speed providing better engine temperatures and a quicker separation from the traffic congestion near the airport. So the slower speed, steeper climb would be better when there are obstacles or high terrain nearby or community noise concerns, but the higher speed, shallower climb would be preferred most of the time because the plane is more controllable at the higher speeds, gives the pilot more energy to maneuver suddenly if he needs to, and it is easier on the engines because they don’t get cooked. Making the judgement of when to use each technique is the hard part if you are new to flying and just learning. Too many choices can increase confusion, reduce confidence, and cause frustration. I’m not a dogmatic instructor so that is why I prefer advanced student/clients seeking higher ratings or transitioning into more capable planes presenting more options over a simple trainer. They have enough experience to appreciate the nuanced choices that a greater number of options presents.


Landing Runway Three Two at Palm Spring airport

At the FAA safety seminar I attended recently they were discussing density altitude and the different things to be aware of. I brought up the performance of the engine and needing to lean for best power. And, asked to explain the mixture lever to a kid that was there as a possible pilot, I went through the basic operation. Then I pointed out that when they taught the fighter pilots in the Pacific theater how to fly their P-51 Mustang aircraft they didn’t teach them about leaning the misture. It took a visit from Charles Lindbergh and a little classroom talk from him, but then they were all doing it and it doubled the range of the strikers. It doubled the reach of our most destructive weapons in the battles. That seemed crazy to me until I remembered that most of the pilots were eighteen and nineteen years old and had just learned to fly. The machines that they were being put into were hugely powerful tail draggers with really effective controls. One up at Camarillo a few years back killed the lightly experienced pilot when he wasn’t happy with his landing and he pushed the throttle full forward to go around. The torque was so great with full power that the plane just rolled over on him and crashed into the ground.


Preparations for departure, Friday Harbor

And I think that a lot of the Old Wives Tales are from that era, when they were trying to teach hundreds (thousands?) of kids (really, kids) how to fly these machines that were at the leading edge of aviation technology. Saying “don’t shock cool the engine in a descent” and “fly squared” (which means the number of inches of manifold pressure should be the same as the number of thousands of RPMs on the propeller), is just a lot easy for a student pilot to absorb.

When the airlines started examining the accidents they were having, they discovered that a lot of them could have been avoided if the resources of having two pilots on board were better utilized. They standardized a bunch of behaviors under the name Crew Resource Management. There are ways that you assign tasks to the Pilot Flying and the Pilot Not Flying, how you communicate intention and suggestions between the two roles, and what to do in emergencies. One of the things they do in professional cockpits are callouts. If you fly with me you will hear me do some of the callouts I was taught in my multi-engine training. One of them is “rotate” when the plane is rolling at the speed it can start flying. The next one is “positive rate, gear up,” when the climb rate is a few hundred feet a minute and it is safe to pull up the landing gear. (Even for that one, as Tim points out, you have to measure the risk. The gear contributes a lot of drag and the moment it is safely stowed in the belly of the plane we pick up airspeed, a margin of safety added with every knot. But if something goes wrong and we come back down, there isn’t usually time to drop the gear again.)

I don’t raise the landing gear until it is no longer possible to land on the runway. The gear switch is the go-no go factor deciding whether to pull back the remaining engine and land, or continue, dealing with the engine-out as a normal inflight emergency. For me, this compartmentalization simplifies what action will be required. If you admit that it will take you 5-8 seconds to actually realize an engine has failed, you start to appreciate 5-6000′ runways that give you more time to build altitude to deal with the engine out actions. As long as you have available runway, you can pull back all the power levers and land on the remaining runway.

As I was earning my multi-engine rating, one of the things they taught at Angel City Flyers was that just before raising the gear, tap the brakes to stop the wheels from rotating, so that they don’t scuff the interior of the landing gear wheel wells. I was bemoaning my poor piloting of the new plane, that I hadn’t even been able to remember to tap the brakes on take off:

This may be a myth or a legend from some old airliner with poor sound proofing and skittish passengers.  I believe the DC-3 had wheel contact between the tire and the aircraft structure so you would want to snub off the rotation before it transmitted a noise up to the passengers. I don’t believe the tires touch any aircraft structure on modern planes. You can ask your mechanic to check during your next maintenance visit. I’ve never seen it in the POH or operating wisdom for any of the light, general aviation planes we are likely to fly. I’ve never see a wheel spin for more than a few seconds after the wheel leaves the ground on a Cessna or Lake Amphibian where you can see the wheels. Usually there is residual drag from the disk brake pads that stop the wheel rather quickly. There are no springs pulling the disc brake pads off the rotors like there are retraction springs on old-fashioned drum brakes. I’ve never tapped the brakes on any of the retractable planes I’ve flown.  

There is no way that I would be able to accumulate the knowledge that Tim has. But by exchanging thousands of words in email I have begun to plot the grey areas in my previous instruction, and correct some of the misinformation I have received. In a community that is as small as aviation, finding people like Tim who are willing to share their knowledge is invaluable.

I have over a hundred hours in the Twinstar model now. That makes me feel much better about each flight and my ability to learn more.

About Colin Summers

I am an architect, programmer, private pilot, husband and father. A couple of those I am good at.
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7 Responses to The Grey Area

  1. Dave Passmore says:

    I really enjoy reading your blog posts, but as a DA42 owner and MEI, I wanted to comment:

    1. If you check Diamond’s official manufacturer’s checklist for the DA42, under “After Take-Off Procedure” the first item is “Brakes…APPLY” right before “Gear….UP.” So tell Tim that Diamond recommends applying brakes before raising the gear right after takeoff; it’s actually not a myth for your aircraft.

    2. You may be confusing Blue line (Vyse) with Red line (Vmc) airspeeds. You never want to get slower than Red line (to prevent loss of control if you lose an engine), but it’s OK to get slower than Blue line (best single-engine climb speed) when landing to reduce landing rollout and distance. You’ll find that on all DA42 models rotation speed (Vr) is faster than Red line, even if the plane wants to fly and lift off the runway before Vr; by holding the plane on the runway until Vr, you’re safely flying above Red line. As soon as you rotate the plane will accelerate, which puts you even further above Red line.

    3. Opinion: After takeoff it’s better to immediately climb, than to level off and accelerate in ground effect and then climb. If you lose an engine after takeoff you can maintain a higher energy state by converting higher altitude to airspeed via “the big push,” rather than by trying to convert higher airspeed (where drag increases as the square of velocity) to altitude. So I disagree with some twin pilots who accelerate in ground effect for maximum airspeed and leave the runway environment at a lower altitude.

    • I have corrected (and annotated) the post. I need to think more about tapping the brakes, since Tim’s explanation of the brakes on small planes makes a lot of sense to me. I think I will paint a line on the tire and see if I can get Angel City to film my takeoff, to see if we can see if the wheels are spinning before I raise the gear.

      At the moment I am climbing I have right rudder in. Shifting my feet so that I can tap the brakes is awkward and I’ve gotten a little wiggle each time. For passengers, I hate having a wiggle.

  2. See? Fascinating stuff. And you are correct that in my head blue line and red line have merged into one, even though I know they are different and that blue line is not as dangerous. More study needed. I think this week I am flying the simulator a little.

  3. Your comments are valuable, by the way. I have no problem being wrong in my posts and being corrected. I never learn more than when I am wrong.

  4. Finn says:

    Red line is just the Vmc when the dead is raised to 3~5 degrees; the real Vmc is a steep function of the delta away from that optimal 3~5 degrees. For example, with wings level and one engine suddenly quits, the Vmc for that moment could be 68 + 3*3~ 77kts; while turning with a 20 degrees into the bad engine that suddenly quits, the real Vmc could be 68 + 3*23 ~ 137 kts. The grey area perhaps explains why so many experienced pilots, including DPEs, CFIs, ATPs, were involved in fatal crashes, especially during training for SE operations.

    • I had never considered that and it certainly explains the crash in Long Beach (King Air, well-trained pilot, losing an engine on take off on a *really* long runway). If you don’t raise the dead engine, correct with the rudder and secure the failed engine, that airspeed is going to drop under Vmc pretty quickly, I would think.

      • Finn says:

        Not just airspeed dropping, but also Vmc is dependent strongly on the banking angle; most POHs appear to bluntly follow the FAR’s definition of a constant Vmc, giving pilots a false sense of security outside the redline, the blue line, or the non-critical engine. This presentation explains well of the bank-angle-dependent Vmc:

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