"Wind check."

How often have you heard this over the radio from an airplane on short final? It's a legitimate request, and Tower is happy to oblige with the current readings. Of course, the sensors may be up to a mile away from the landing threshold.

There is a more direct way to know the current wind at your location: lakes. Runway 7 has a lake just to the right. Runway 25 has a lake right under you. These reveal local conditions in real time.

We all know intuitively there are two obvious indicators of wind direction -- waves and streaks. The wind is perpendicular to the waves, but which of two opposite directions? Don't try to read the direction from waves, because there are illusions which will flummox the closest observer. And streaks: the wind is parallel to the streaks, but again, from which of two opposite directions does it blow?

The answer is to look for the calm edge of the lake. The calm edge indicates the direction from which the wind is blowing. The air can't curl over the bank fast enough to disturb the upwind edge of the lake, and it looks like a mirror compared to the disturbed surface.

Now that we know the direction of the wind, what is the velocity?

If there are mere waves, nothing else, this indicates a wind velocity from 3 to 8 knots. If there are amorphous streaks (you'll know these when you see them -- they are, well, amorphous streaks and shapes hard to describe verbally but sailors would recognize them as a freshening wind), this indicates a wind velocity from 8 to 12 knots. If there are lines of white bubbles parallel to the wind, this indicates a velocity more than 12 knots. A sailor would recognize these as whitecaps. Lines of white bubbles combined with a cloudy, disturbed surface? That's 18 knots or above.

At first, new pilots describe learning the "feel" of an airplane. With experience, they concede that vision is the most important sense, and from this time they can fly anything with wings without much instruction. Learn to read the surface wind, from lakes and smoke and the direction birds land and take off.

First, be safe.

John Nadon
CAP Chief Pilot

Comments: nadon@aya.yale.edu

What's the red knob do?

For some, it's something to be arbitrarily pulled back a bit when taxiing. And maybe in cruise, it should be fiddled with -- pulled back some other, arbitrary amount, at some arbitrary altitude.

The truth is, there's rarely a time the mixture knob can't be used to reduce fuel burns, while simultaneously making the engine run cleaner and more efficiently.

The mixture control is important: it is a way to control power. Yes, power! Don't believe me? As a thought experiment, pull the mixture all the way back -- the engine will stop making power altogether. Now push it all the way forward -- at or near sea level, the engine will produce its full rated power, or very close to it. At all the ranges in between idle cut-off and full rich, the amount of power made by the engine will vary. So, there's no denying that the mixture control has a direct effect on power, not to mention EGT (exhaust gas temperatures) and CHT (cylinder head temperature).

Lean during taxi

When taxiing, leaning the mixture reduces the amount of fuel flowing into the cylinders, which in turn reduces the chance of fouling the spark plugs. Most of us understand this, and most do lean on taxi, but how much? Many pilots simply pull the mixture control back a quarter inch or so, and leave it at that. But, think about this: there's no way to harm a normally aspirated reciprocating engine running at or close to idle power with the mixture leaned all the way back to the point that the engine runs slightly rough, and then pushed forward again until smoothness is achieved. This setting is usually far more aggressive than what most pilots use for taxi.

What's the benefit? Well, you'll burn a bit less fuel on taxi, sure. But more importantly the engine will be running cleanly at low RPM. Chances are your mag check will go smoothly, and you won't have to "clear" the rough mag at high RPM in the runup area.

There's one other advantage. Have you ever forgotten to bring the mixture back to full rich for takeoff? Well, if you make that mistake with the mixture leaned as described above, when you go to apply takeoff power the engine will simply cough a few times and stop running thanks to an excessively lean mixture. It might damage your pride a bit, but at least you won't be taking off with the mixture control set improperly, which is clearly unsafe. (Besides, as soon as the astute pilot notices the engine start to cough, he'll simply bring the throttle back, enrichen the mixture, and continue the takeoff.)

Low-altitude leaning

Obviously, flying near sea level in Florida, we set the mixture to "full rich" for all takeoffs. But when should we lean during climb? Popular flight training wisdom suggests that the mixture should not be leaned under 3,000 feet MSL. And, there's some merit to this approach from an experience standpoint. Student pilots, or newly rated pilots, may benefit from the reduced workload associated with "not touching the mixture control" at low altitude.  As a CFI, when I see a pilot make this PIC decision, I ask why.  If the answer is, "I want one less thing to worry about right now," or "I'm task-saturated and I'm worried I'll forget it later," etc. I let the pilot know that I don't find fault with their decision. Leaving the mixture full rich at low altitudes isn't "unsafe," it's just not the way the engine likes to run, and it costs you money.

(Aha! Now I have your attention.)

However, if the answer to my question is, "I was told to do it that way," or "I don't really understand when or why I should lean," it's time to have a discussion on the subject.

Leaning Concepts

Leaning is really a simple concept complicated by the fact that engines, airplanes, and instrumentation are different. Some airplanes have no EGT gauge at all, while others are variously accurate and inaccurate. Some engines are carbureted, which makes precise and effective leaning difficult, while others are fuel-injected. What it boils down to is that your technique will be dictated, to some extent at least, by the type of engine you're flying and the tools (instruments) you have available to help you in the cockpit.

The best case scenario is that you're running fuel-injection and have a multi-cylinder electronic EGT/CHT gauge available.  The club's GA-7 Cougar has the latter, but has carbureted engines.  The Cessna 172R (N89005) has a fuel-injected engine with a single analog EGT and CHT gauge (no individual cylinder indications).

Why does it matter?  The short answer is that carbureted engines, despite some advantages over their fuel-injected brethren, don't distribute fuel evenly or precisely.  And, truth be told, although fuel-injected engines are better at fuel distribution simply due to their design, it's "luck of the draw" for an engine fresh from the factory or overhaul with regards to how evenly fuel is metered to the individual cylinders.  (As delivered, both Lycoming and TCM engines also suffer from uneven air induction, but there's nothing we can do about this.)  This problem has been attacked by aftermarket manufacturers selling calibrated fuel-injectors, which aims to even out the fuel distribution and make leaning operations easier and safer.

Why does this matter?  Simple -- when leaning, one cylinder will start running rough before the others, due to the reasons described above.  In a perfect world, all four, six, or eight cylinders would be running at exactly the same EGT and CHTs, and when leaning, those cylinders would all start to run rough at exactly the same mixture setting.  But this never happens, not even in an airplane with calibrated fuel injectors, and definitely not in our club airplanes (or any other airplane without those calibrated injectors.)  It's an ideal which is sought, but never achieved.

So when you lean to the point of engine roughness, know that one cylinder -- usually -- has just fallen below the threshold of a suitable fuel-air mixture which allows it to run smoothly, thus the entire engine runs "rough".

What's really happening here is that one cylinder has been leaned to the point of peak temperature, then below and into a realm of engine roughness.  If you bring the mixture control forward after reaching this point, you are running Rich of Peak.

I'm going to bring up a controversial topic now: running engines "Lean of Peak".  Without passing judgement on the relative merit of this concept, I will say that our club airplanes are not equipped to be run lean of peak.  Without the proper instrumentation and calibrated injectors, we'd be guessing when it comes to identifying "peak" and it would be difficult if not impossible to safely run in that mode.  I don't recommend trying it.

So now that we know we're going to be running ROP, how rich should we run?  This is another controversial topic.  First and foremost, consult the Pilot's Operating Handbook.  Recommended power settings will be found there.  Usually, the recommended range for "Best power" is anywhere between 50 to 125 degrees ROP.  For airplanes that are not equipped with an EGT gauge, we'll simply have to "play it by ear".  Enrichen to engine smoothness and sightly beyond.  Keep an eye on CHT, if the airplane is so equipped, and don't forget that you may have other means of adjusting the cooling of the engine, i.e. cowl flaps on some airplanes.

If you do have an EGT gauge, use it!  It's less important that the gauge indicates a precise temperature, than it is that the gauge can show you trends, or the relationship of one temperature to another.  Generally speaking, even if an EGT gauge is miscalibrated, it will still show the correct increments between two temperatures.  For leaning, this is all we care about -- "peak" will occur with the needle fixed in one location, and 50-125 degrees rich of that point should be correctly indicated by "X" number of increments on the gauge.

If nothing else, remember this: don't choose any mixture setting that causes engine roughness.  That's not good for the engine.

Leaning in the climb

What?  Heresy!  You never lean in the climb, and certainly not at low altitude, correct?

Well, not really.  It's time for another thought experiment.  (Once again, a disclaimer: we're assuming normally-aspirated reciprocating engines in this example.  The club does not currently operate any turbocharged engines; turbos require different techniques.)

Let's think about what happens when we climb.  Let's say we're flying N89005, a Cessna 172R with a fuel-injected, 160bhp engine bolted onto the firewall.  You're cleared for takeoff on runway 7 at ORL.  You make sure your mixture knob is pushed all the way forward, effecting a maximum-rich fuel-air mixture, push the throttle smoothly forward, and start rolling.

Freeze it! With the airpane on the runway, let's glance at that EGT gauge.  (You scan your engine instruments during the initial roll anyway, yes?)  At full power, your EGT should be somewhere between 1100-1400, depending on OAT, but the actual temperature really doesn't matter. The needle will be reading somewhere near the middle of the gauge, pointing at a white line.  That's all we really care about: a baseline measurement.  Take note of where that needle is pointing and file it away for future reference.

You rotate and start climbing out.  A 500 foot check is a good idea; making sure gear and flaps are up.  At 1,000 feet you can consider setting climb power, but in the Cessna 172R it should be full throttle, so there's nothing to do.  This is nice and simple.

Passing through 1,500 feet, let's freeze it again.  Zoom in on the EGT gauge.  What do you think it will show?

Some of you already know the answer.  For those who aren't sure, let's think about it.

Have we touched the mixture knob?  No.

So has the fuel-air mixture been adjusted?  Yes!  As we climb, air density decreases, which means the mixture (which isn't just fuel, correct?) has actually been getting richer with the climb.  There are fewer air molecules inducted into the engine, therefore there's now more parts fuel to fewer parts air.

Yep, the mixture's getting richer, just by climbing.  I suppose you could consider your yoke a "mixture" control, in an indirect sense.

So the answer to the question is this: the EGT gauge will now show a slightly lower EGT indication.  This is not necessarily a bad thing.  On very hot days, with a heavily loaded airplane, the extra fuel can help cool the engine -- and not because the fuel cools the engine by circulating through it!  This is commonly misunderstood.  Running full rich makes for a smoother, slower combustion event.  It delays the "peak pressure pulse" (that nanosecond when the explosion reaches its maximum pressure) and enhances the mechanical advantage of the crank angle.  Without getting too deep into the details, the further from Top Dead Center the PPP occurs, the greater the mechanical advantage, the cooler the CHTs and the lower the cylinder head pressures -- a very important consideration, but we have no gauge in the cockpit to measure this.  The richer you run -- to a point, of course -- the smoother those combustion events occur, and the cooler the engine will run.

But, truth be told, you really need to be flying a maxed out airplane for this to be your primary concern.  If your CHTs look good, you're not holding a ridiculous angle of attack to maintain Best Rate of Climb, and performance seems nominal, there's no need to actually enrichen the mixture -- which you are doing by ignoring the mixture knob -- as you climb.  In fact, going back to the baseline measurement of EGT while the airplane was still on the runway, how could we harm the engine by adjusting mixture such that EGT remains constant in the climb?  Answer: you can't, with the exception/caveat described above.

So if you're climbing out, planning to cruise at 7,000 feet to enjoy the cool temperatures at that altitude enroute to a fun summer destination, consider maintaining a constant EGT all the way to altitude.  You'll save fuel, the engine will be happy, and you'll be able to afford a few more $100 hamburgers.  Furthermore, even if you're cruising at a low altitude -- below 3,000 MSL -- don't ignore the mixture knob!  Especially when you're at a cruise power setting rather than full power: the engine doesn't require a full rich mixture.  In fact the only time you absolutely need full rich is on takeoff at sea level!  It makes sense when you think about it: if the engine was okay at full RPM and full rich on initial climbout, why would it still require such a rich mixture when you reduce power to, say, 2100 or 2200 RPM?

Fly safe out there!

Ryan Ferguson is a CFI/I and MEI for the CAP Flying Club.  He can be reached via email at ryan@hawkerpro.com or (407) 920-7660.

In Part I, we discussed single-engine VFR briefings.  In Part II, we'll tackle IFR and multi-engine.

Clearly, when departing IFR, our planning horizon needs to be adjusted.  We now must be aware of our aircraft's ability to meet the performance requirements of any assigned ODPs or SIDs, we must configure the cockpit to fly any required courses or routes, and we must know we can reach our clearance limit with IFR fuel reserves on-board.  A good briefing considers all of these factors at minimum, and a better one includes a forecast of where the aircraft will be flown in the event of an emergency.

Factors which may impact your decision-making in the event of an on-departure IFR emergency:

1) Bases.  Very low ceilings limit opportunities to choose an off-field landing site in the event of an engine failure in a single-engine airplane.

2) Available VFR weather at nearby airports.  In the event of an electrical failure, can you navigate to an area of VFR conditions?  Dead reckoning and basic pilotage skills may play a role here, but if you don't know where the VFR conditions are to be found before departure, you won't able to find them.

3) Do you have a handheld GPS on-board?  Many modern handheld GPSs offer phenomenal capabilties, even the ability to fly an "instrument approach" -- only to be used in emergency situations, of course.

The pilot's decision-making and planning is more complex when departing IFR in a twin such as our Gulfstream American Cougar (GA-7).  Now the pilot must decide whether his/her single engine performance is sufficient to a) continue the departure procedure or provided instructions via clearance, b) be able to maintain an MEA and c) execute a single-engine approach and landing back at the departure airport, or if necessary, a different airport.

What's most important is that the pilot considers his/her options on the ground before departure rather than in the clouds.  An old Air Force saying:  Prior Planning Prevents Poor Performance.  It is true in instrument and multiengine flying, as well as all other walks of aviation.

If you expect the unexpected, you will never be surprised.  Fly safe.

-Ryan Ferguson
ATP/CFII/MEI
ryan@hawkerpro.com
Questions? Need a CFI? Call anytime: (407)920-7660

To instructors and students,

All flight students who are not citizens of the USA must register with TSA's Alien Flight Student Program before beginning flight training. This should be done online. I don't have the address at hand, but if you google AFSP you will find your way there.

Independent CFIs (such as we) giving instruction to foreign students must register with AFSP also.

Here's a little-known trap: Even if your student is a USA citizen, he must still present a passport (or birth certificate plus state-issued photo ID) to his instructor, who must then endorse the student's logbook that these documents have been produced. Additionally, the instructor must keep records of such endorsements for at least five years.

Instructors please note: You are not endorsing that the student proved his citizenship, only that the documents were presented to you.

And note also: These rules apply only to those who seek a private pilot certificate, an instrument rating, or multi-engine training. Oddly, students seeking the commercial certificate are not included in the regulation.

John Nadon
CAP chief pilot