Interesting Article

[Colonel Sanders]

I know good low time instructors, and I know some really bad high time instructors

Sure, there are always spectacular exceptions to the
rule, but our entire ICAO system of pilot licensing is
based on experience, which is supposed to be reflected
in the resulting skill and knowledge.

Yes, I know there are people with 20 years of experience
who really have 6 months experience 40 times over. Can't
do anything about that. That's pretty much the textbook
definition of stupidity. Yes, there are people on the left
hand side of the IQ bell curve. Got that.

But who would you prefer to cut on you: a surgeon with
the ink still wet on his diploma, or one with 10 years experience?

If you want a lawyer to represent you in court, would you
like someone right out of school, or a guy with 15 years
of court experience?

You could argue the same thing about plumbers and electricians.

Yes, there will always be stupid people in the world, but that
doesn't stop the rest of us from learning as we get experience.

All you need is 200 hours and you can be a flight instructor.
That's awfully green, IMHO. Too green.

[akoch]

Do the trig - it's not much. I might recommend you
pump your tires up to nominal. I do love scuffing the
sidewalls!

And remove the wheel pants. What Colonel is looking to do is just not going to happen, or you leave your new shiny wheel pants behind sitting on the runway at your touchdown point.

[photofly]

Do the trig - it's not much. I might recommend you
pump your tires up to nominal. I do love scuffing the
sidewalls!

Ignoring the sideways force from the deflected rudder (which I think is small and in any case acts with the lift) the sideways force is equal to the vertical component of lift times the tangent of the angle of bank. If you have one wheel on the deck, the lift is less than the weight of the aircraft because of the upward force on the tire. Let's estimate the tire is supporting 25% of the aircraft weight (half of what it would while stationary, since normally both wheels are on the ground) and the bank angle is 10 degrees.

For an aircraft at 2950lbs the side load on the one tire and wheel bearing is therefore nearly 400lbs.

I have no idea what the side load rating for a typical light aircraft u/c is, probably quite high, to cope with lousy cross-wind landings.

[Colonel Sanders]

Scuffing the sidewalls is analogous to what we in
the sportbike world refer to as "chicken strips":

[Beefitarian]

This is the critical point I think. When it comes down to it I feel the test standards are set really low. This would also be the simplest area to improve things with results. Something simple like bringing back the old 0-5 grading system would improve things by leaps.

How do they grade now?

I think a 0-10 would be better to be honest. A 6/10 tells me more about how close you are than a 3/5.

[Colonel Sanders]

Let's estimate the tyre is supporting 25% of the aircraft weight (half of what it would while stationary, since normally both wheels are on the ground) and the bank angle is 10 degrees.

Ok, the Maule was 1700 lbs when I did that to the sidewall, and 25%
of that is 425 lbs that the wheel is supporting. With a bank angle of
10 degrees we are looking at sine(10) = 0.174 for the sideways
component. So, 425 x .174 = 74 lbs

I got lots different numbers than you.

[photofly]

The wheel is resisting the sideways lift, so its side-load is a fraction of the unsupported weight and not of the weight on the wheel. And its the tangent of the angle and not the sine, because the known side of the lift triangle is the adjacent (the vertical component of the lift) and not the hypotenuse (the total lift).

For the maule under those circumstances the side load is 225 lbs.

[Colonel Sanders]

Meh. I'm still suspicious of your numbers - they
might be high enough to roll the bead off the rim.

Mine are just enough to lightly scuff it

[Shiny Side Up]

Sure, there are always spectacular exceptions to the
rule, but our entire ICAO system of pilot licensing is
based on experience, which is supposed to be reflected
in the resulting skill and knowledge.

I ain't talking about exceptions to the rule though, and if you plotted out who is good and who is bad you'd end up with more of a shotgun pattern than a bell curve. The main reason for this is that bad instructors have been draw from the pool of pilots whom there are a fair ammount fo bad ones within. In all of your examples length of experience isn't the only thing that constitutes who is good at what they do. In my experience, people just don't learn that well from time repeating stuff, human beings are notoriously poor learners. If pilot experience vs skill really ended up on a bell curve, we wouldn't be having this discussion.

All you need is 200 hours and you can be a flight instructor.
That's awfully green, IMHO. Too green.

IMHO that depends on the individual. Something to think about: currently the testing standards are grotesquely low for all of the licensing standards. A pilot with even thousands of hours could probably phone it in and pass the instructor rating. In a majority of the new class 4s and some of the class 3s that I have interviewed - and not hired - most of these guys, regardless of their experience level, shouldn't even have passed the test. That to me is the real problem - there's no penalty for doing shitty.

[Shiny Side Up]

This is the critical point I think. When it comes down to it I feel the test standards are set really low. This would also be the simplest area to improve things with results. Something simple like bringing back the old 0-5 grading system would improve things by leaps.

How do they grade now?

I think a 0-10 would be better to be honest. A 6/10 tells me more about how close you are than a 3/5.

Its on a 1-4 scale. You have to really screw up to get a "1" or fail on an excersise and fail the test. Its no longer possible to fail the test by doing really crappy, but not outright failing. The test still has the same score mark as it did before. The CPL test ups the ante a bit, but not by much, since they're slightly lowered the standards if you do an integrated program.

[iflyforpie]

For the maule under those circumstances the side load is 225 lbs.

Meh. I'm still suspicious of your numbers - they
might be high enough to roll the bead off the rim.

Mine are just enough to lightly scuff it

I weigh 225 lbs give or take... and I have to jump up and down on a worn out DEFLATED tire to break the bead (I know you can get bead breakers... I like the exercise). 225 lbs of side load is nothing for a tire... and I'm pretty sure you are nowhere near that if you are just dragging it on the ground.

[Colonel Sanders]

Buy a bead breaker, you cheap bastard!

(I don't have one, either. Ahem).

His original sideloading number that I was referring to was:

nearly 400lbs

which, as I said before, sounds suspiciously high for
just the sideloading, at a tiny bank angle of 10 degrees.

[photofly]

Meh. I'm still suspicious of your numbers - they
might be high enough to roll the bead off the rim.

Mine are just enough to lightly scuff it

It gets worse: at 20 degrees of bank your Maule tyre is pushing sideways at 460lbs. However, if you unload the wing and put more weight on the tire the side-load decreases in proportion.

If you're suspicious of the physics, think of it like this: without the contribution of the tire the aircraft would be in a banked turn, accelerating sideways. Since it's travelling in a straight line the wheel is reacting sideways to resist.

225 lbs of side load is nothing for a tire

Does it make any difference when the wheel is rolling at 60mph? I don't know. Dynamic deflections in tires can be signficant.

and I'm pretty sure you are nowhere near that if you are just dragging it on the ground.

The colonel was the one who suggested doing the math. I'm open to an alternative analysis, but gut feelings, not so much.

sounds suspiciously high for
just the sideloading, at a tiny bank angle of 10 degrees.

A very good friend of mine recently suggested "Do the trig" ... so I did.

[Colonel Sanders]

Ah, ok, I think I understand. You are looking at
the lift vector. I keep drawing the force vectors
at the tire, and I keep getting sine in my picture.

[Colonel Sanders]

Looking at the lift vector .... assuming that the wings
are producing 1000 lbs of lift at 40 mph (wild guess)
then I think you are saying that we incline the lift vector
of 1000 lbs 10 degrees.

My inclined lift picture has the hypoteneuse as 1000
(lift) and the opposite as the vertical component of
lift, and the adjacent as the nasty horizontal component
of lift (scrubbing sidewall). Therefore

cosine(80) x 1000 lbs = 173 lbs

My number of 1000 lbs of lift was pulled out of a hat -
it might be considerably less than that, because the
AOA is much less than Clmax.

If lift was say 500 lbs, we would get 86 lbs sideforce.

[Beefitarian]

Its on a 1-4 scale.

That's pretty bad. Might as well make it out of 2. Pass or almost pass.

[photofly]

The force vectors acting on the tire will tell you if the tire will slip sideways, which is most likely to happen when the vertical force on the wheel is least and the sideways force is greatest (both of which occur when the aircraft is almost entirely airborne).

In order to stop the tire slipping you're going to have to put some significant weight on it, which has the effect of unloading the wing and thereby reducing the sideload.

Maybe when you're doing this exercise you're putting a larger fraction of the a/c weight on the wheel than I estimated, which would help the tire out considerably.

cosine(80) x 1000 lbs = 173 lbs

Sine (or cosine) if you estimate the total lift, and tangent if you start with the vertical component that's holding the weight of the aircraft. Within the bounds the exercise here I'd agree with your calculation of a couple of hundred pounds at 40mph; if in a faster heavier aircraft then a lot more.

When I last flew the exercise it was in a Champ and I recall the guy at the controls (wasn't me) had quite a lot of forward stick, which would reduce the angle of attack, load up the wheel vertically and reduce the side-load considerably. I suspect that's the answer.

On the other hand, to reduce the aerodynamic AoA to zero (no lift) and remove *all* the side load you'd have to put the entire weight of the aircraft on one wheel - more than double what it's designed for. And you've got the wheel at an angle so the load will be carried more on the outboard bead than the inner.

[Colonel Sanders]

On the other hand, to reduce the aerodynamic AoA to zero (no lift) and remove *all* the side load you'd have to put the entire weight of the aircraft on one wheel - double what it's designed for.

That's a lot simpler calculation.

Assume the wing produces zero lift (ahem).

All of the aircraft's weigth (1700 lbs) is on
one main. Obviously of the aircraft is level
(a bit of a trick) there is zero sizeload and
the entire force is parallel to the normal axis
of the aircraft.

But if we incline the aircraft, we end up with
a force triangle with the entire weight of the
aircraft (1700 lbs) as the hypotenuse, with
the opposite still parallel to the normal axis
and the adjacent perpendicular to that (ie
sideload) gives:

sine(80) x 1700 = 1,674 lbs (parallel to normal axis)
cosine(80) x 1700 = 295 lbs (perp to normal axis)

I had figured, in my usual back-of-the-envelope
way, that both numbers above would be reduced
by the production of lift. Hm.

[photofly]

You've actually pointed out (perhaps inadvertantly) a problem with the previous simple analysis. The side-load exerted on the runway surface was correctly calculated, but the wheel is tilted (at the angle of bank, near enough) to that plane.

So both the earth-vertical and earth-horizontal forces on the wheel have a component normal to the axle (which the wheel is designed to take) and a component parallel to the axle (which we want to avoid).

Let alpha be the fraction of the weight of the aircraft on the wheel, and theta be the angle of bank. Then:

-The earth-vertical force on the wheel is alpha.g.m. This is acting inboard on the tire, trying to push the tire towards the fuselage, at an angle theta. So the side load from this component is alpha.g.m x sin-theta

-The earth-horizontal force on the wheel is (1-alpha).g.m.tan-theta. This acts in the same direction on the tire, also trying push the tire off the inboard rim. The side load from this component is therefore (1-alpha).g.m.tan-theta x cos-theta

The total inboard force on the rim is the sum of the two. Both parts have a factor of g.m, the weight of the aircraft. The other part depends on alpha and theta and is:
alpha.sin-theta + (1-alpha).tan-theta.cos-theta
=
alpha.sin-theta + (1-alpha).sin-theta
=
sin-theta

So the side load doesn't actually depend on how much weight is on the wheel. That seems counter-intuitive, but is it correct?

What it appears to mean is that as you load up the wheel, the side-load from the weight of the aircraft on the angled wheel exactly makes up for the reduced side-load resisting the sideways slide of the aircraft. I think that makes sense.

For a 10 degree bank the side load is 17% of the a/c weight, regardless of whether the aircraft is almost entirely flying, or hardly flying at all.

[MikeGolfEcho]

While I try and get my head around the math above, may I go back to an earlier question (and my initial query when posting the article link), is more tech in the cockpit leading to sloppier flying (by instructors and their respective students) and is this sloppier flying negating the potential safety benefits of having said tech in the cockpit?

I'm also now really curious about the evolution of instruction regarding heli vs fixed-wing. How and where did this difference start, I'm guessing Second World War? I totally get the difference in complexity of machinery, but both will kill you just as dead.

Appreciate all the input

[Shiny Side Up]

is this sloppier flying negating the potential safety benefits of having said tech in the cockpit?

The thing to remember is where the tech increases safety has nothing to do with where sloppy flying decreases safety. A majority of the increases in safety that have been derived from all the gizmos - GPS in particular - have reduced all of those accidents that primarily have occured due to problems enroute. Largely those problems stemmed from pilots getting lost or losing situational awareness and eventually contacting the ground because of it. People still get lost with the assistance of GPS and still run out of fuel with them, but for the most part the tech has helped compensate for typical pilot deficiencies in these areas.

I'm also now really curious about the evolution of instruction regarding heli vs fixed-wing. How and where did this difference start, I'm guessing Second World War? I totally get the difference in complexity of machinery, but both will kill you just as dead.

Keep in mind that helicopters didn't become common until well after the second world war, which was sort of the crucible for developing most fixed wing flight training. This meant that helicopter flight training was able to evolve somewhat independantly. Also given the numbers of pilots trained and the numbers of helicopters vs fixed wing aircraft, the collective military is still the largest trainer of helicopter pilots world wide. That means there is probably still a larger number of helicopter pilots who were trained "right" shall we say, in the pool than by somewhat less regulated civillian sector, and a higher percentage of this type of pilot engaged in the training process. Those factors of course aren't the only ones at play.

[Colonel Sanders]

What it appears to mean is that as you load up the wheel, the side-load from the weight of the aircraft on the angled wheel exactly makes up for the reduced side-load resisting the sideways slide of the aircraft. I think that makes sense.

For a 10 degree bank the side load is 17% of the a/c weight, regardless of whether the aircraft is almost entirely flying, or hardly flying at all

Isn't that neat! it boils down to an incredibly simple sine
of the angle of bank, regardless of speed.

However, I will have to start respecting tire manufacturers
more - it looks like I did have a sideload of 300 lbs (!!).

http://i.imgur.com/1AsSM.jpg

As IFP points out, it's all that us 200+ pounders can do, to
break the bead on an uninflated tire, jumping up and down
on it. An additional 30 psi would certainly help hold the bead
on.

One practical consideration is that I want to avoid the tire
"creeping" on the rim, which is the rubber part slowly rotating
on the metal part, generally caused by hard braking with low
tire pressure. The problem with "creeping" is that you can shear
the valve stem, which causes the tire to suddenly deflate.

Hence my recommendation that the tires be pumped up to
at least the manufacturer's recommended pressures, before
one-wheel landings.

[akoch]

I think sloppy flying refers more to the basic airplane controls - airspeed, attitude, altitude, turn coordination, mixture, landings/takeoffs etc. So all the things where the tech does not come into play that much if at all.
The better electronics helped with navigation, situational awareness, traffic avoidance etc. And I personally think is has been a considerable change for the better. Does not mean that these things completely took over, but as tools they do help a lot imho.

[MikeGolfEcho]

I think sloppy flying refers more to the basic airplane controls - airspeed, attitude, altitude, turn coordination, mixture, landings/takeoffs etc. So all the things where the tech does not come into play that much if at all.
The better electronics helped with navigation, situational awareness, traffic avoidance etc. And I personally think is has been a considerable change for the better. Does not mean that these things completely took over, but as tools they do help a lot imho.

I can see they can help a lot, but not to those poor unfortunates who need it to navigate their way around the circuit and to judge their taxiing speed. I guess it comes down to quality of instruction again - how to use things properly. I can see how checking your position on a map with a GPS would be a handy tool, but I think maybe they should be introduced later on in a pilots' life, like when they've got some stick and rudder skills and done some cross country using dead reckoning and pilotage alone. Then again, what do I know?

[akoch]

I don't have much insight into the flight training other than finishing mine about a year ago. So can't say how typical is that to see the students checking the taxi speed via GPS or using it to fly the circuits. It is just such an extreme example. But then who knows. From my perspective I don't get it, what can be simpler than just looking outside and it is in front of you.

But I do remember, that when you are a student who just got to his first solo 10 miles "cross country" flight and learning to find an airport... your eyes are not trained yet to spot those lines on the ground, everything looks weird, you might be like me who's English is far from first or even second language so everyone is talking wierd on the radio , and there is a bit of haze so the mountains and landmarks are not that prominent.... Trust me, you don't mind the GPS at that point in time. Then, as you get more comfortable and you are able to do more things without thinking, you free up the CPU cycles for other things like scratching your head and looking through the paper map that is larger than the cockpit space. Also the airspace here in Vancouver does present some challenges to the newbees.