Be a Better Pilot

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Zaibatsu
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Re: Be a Better Pilot

Post by Zaibatsu »

Big Pistons Forever wrote:
Zaibatsu wrote:Your airspeed should be +1/2 the gust and -0. Fly faster during gusty conditions since it will give you more margin above the stall and more positive control. Plan a longer round out and roll out and try to time touchdown between gusts.

Adjusting airspeed by applying the gust factor correction is a large aircraft SOP and so care should be taken when applying it to small aircraft. Large aircraft have lots of inertia and therefore take time and distance to recover lost airspeed or shed extra airspeed. Light aircraft have much less inertia and therefore less requirement to have a speed buffer.
Small aircraft don't have SOPs... but there are many factors of airmanship which apply to light aircraft that aren't written in a checklist or POH. Also, larger aircraft have more inertia and are less likely to LOSE airspeed rapidly in a case where wind is changing rapidly (we're talking gusts, not performance reducing wind shear). They'll gain speed with a gust, but it won't decay as much when the gust stops.
The gust factor formula is also not recommended or supported in any of the light Cessna or Piper POH's that I have ever seen. The only mention of increasing speed I have found is in the Cessna POH. It notes that for short field approaches slightly higher approach speeds should be used in turbulent conditions.
Like many other formulas. You won't find a 1/60 rule in a POH. Nor a 100 RPM = 100 FPM descent.
For the Cessna 172 which is the airplane I referenced as an example in my original posts, the POH "Normal Operations" section gives a range of recommended approach speeds. They are 65 to 75 knots with no flap and 60 to 70 knots with 30 deg flaps. Therefore in my opinion this aircraft should never be flown at an approach airspeed faster than the upper range of the recommended values as they will provide a adequate margin above stall on all circumstances. If control at these upper range speeds feels doubtful then I would suggest that conditions are so extreme it is time to find another place to land.
Sounds like it is in line with what I'm saying. A ten knot spread equals the range to deal with 20 knot gusts... more than I'm comfortable in in a 172.
I think it is also important to note that these speeds are for gross weight. They will be to fast at lower weights. A pretty good rule of thumb is for a typical landing in a Cessna 172 or Piper Cherokee with 2 persons and half tanks reduce the gross weight approach speed by 5 knots. If you use the formula to adjust approach speeds you will find that the 5 knots reduction will pretty close to the calculated speeds for all your typical light fixed gear singles.
Speaking of things that aren't in the POH or approved by Cessna or Piper. :wink:
Watching landings my observations is that most landings I see are flown too fast resulting in excessive float and/or flat or even nose wheel first landings. Adding extra speed to the approach does not make it safer, in many case it increases the degree of difficulty and the likelihood of aircraft damage.
Yes, but those aren't because of gust additions, they are speeds that are too padded in calm or steady wind conditions. 20G30 means that your 60 knot approach in a 172 turns into 65. The float fests happens at 70 or 80 knots.
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trampbike
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Re: Be a Better Pilot

Post by trampbike »

Zaibatsu wrote: Also, larger aircraft have more inertia and are less likely to LOSE airspeed rapidly in a case where wind is changing rapidly (we're talking gusts, not performance reducing wind shear). They'll gain speed with a gust, but it won't decay as much when the gust stops.
So?
BPF point still stands.
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Zaibatsu
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Re: Be a Better Pilot

Post by Zaibatsu »

What point?
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Big Pistons Forever
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Re: Be a Better Pilot

Post by Big Pistons Forever »

Zaibatsu wrote:
Yes, but those aren't because of gust additions, they are speeds that are too padded in calm or steady wind conditions. 20G30 means that your 60 knot approach in a 172 turns into 65. The float fests happens at 70 or 80 knots.
I think we are saying the same thing in a different way. In your example above you are adding a gust factor to an approach speed for the bottom end of the POH range of recommended speeds or the speed you would want to use in no or light winds and smooth conditions. The upper range of the recommended speeds, 70 kts is what would be appropriate for high gusty winds and turbulent conditions and is addressed in the Normal Operations section of the C 172 POH by the advice to increase approach speeds for those conditions.

The problem happens when you use an upper range approach speed and then add a gust factor correction. This was my concern with your advice to
Your airspeed should be +1/2 the gust and -0.
That only works if you understand what approach speed you are applying it to. Unfortunately I see a lot of flying schools giving students a one size fits all approach speed to use on every approach and this speed is usually at the upper range of the POH speeds.

My concern is somebody reading this and deciding to apply this gust correction factor without consideration or perhaps a full understanding of what speed to apply it to.

My personal observation is that the majority of C172 landings I have witness of the last few years were flown at a speed higher than desirable as evidenced by a flat or even nosewheel first touch down or a proper tail low touchdown well down the runway after an excessively long float.

Anyway a good discussion and I hope food for thought to those reading this thread.
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Gannet167
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Re: Be a Better Pilot

Post by Gannet167 »

Most large, higher performance planes will fly a very specific speed on approach. Generally, it's 1.3Vs which allows a safe margin above stall on approach but also allows for minimal flare and keeps landing distance reasonable. This speed, Vref, would be calculated based on pressure altitude, temperature and landing weight; for every landing. If your Vref is 140 kts and there's a 15 kt gust, you could find yourself seeing as low as 125 kts indicated momentarily, which might be getting excessively slow on approach. Hence, a gust factor is applied to provide some safety. In a Cessna, Vref might be something like 60 kts, painfully slow especially with any headwind sk the approach speeds typically flown in a Cessna are well above Vref. So applying a gust factor may be overkill, since you're never close to stall at 75 or 80 kts on approach (assuming 1G), as it's more like 1.7 Vs.
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fixedpitch
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Re: Be a Better Pilot

Post by fixedpitch »

The upper range of the recommended speeds, 70 kts is what would be appropriate for high gusty winds and turbulent conditions and is addressed in the Normal Operations section of the C 172 POH by the advice to increase approach speeds for those conditions.
So does this mean everything I've been taught on handling the C172 in gusty conditions is wrong? I've been using that formula for years. If it is incorrect, then it's good information to know. Typically I will come in without flaps (assuming strong gust conditions with headwind component) using the gust formula noted above.
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Big Pistons Forever
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Re: Be a Better Pilot

Post by Big Pistons Forever »

fixedpitch wrote:
The upper range of the recommended speeds, 70 kts is what would be appropriate for high gusty winds and turbulent conditions and is addressed in the Normal Operations section of the C 172 POH by the advice to increase approach speeds for those conditions.
So does this mean everything I've been taught on handling the C172 in gusty conditions is wrong? I've been using that formula for years. If it is incorrect, then it's good information to know. Typically I will come in without flaps (assuming strong gust conditions with headwind component) using the gust formula noted above.
If the approach speed you are using in calm wins allows for a smooth tail low touchdown after a short float than it is the correct speed for benign conditions. Applying the formula above would then be appropriate for gusty and/or turbulent conditions, as long as you do not exceed the upper range of the POH approach speed for gross weight or that speed corrected down for lower weights.

The bottom line is how the landing goes. If there is a protracted float with you fighting to keep the aircraft on the centre line and hold the correct landing attitude then you are approaching too fast.

In any case what ever speed you choose don't force a bad approach, go around if things start unraveling and try again. I would guess that in almost all light airplane landing accidents there numerous ignored indications that this was not going to end well and numerous opportunities to do an uneventful go around
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waterdog
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Re: Be a Better Pilot

Post by waterdog »

BPF

New pilot, awesome original post.

Thanks for posting!
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boogs82
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Re: Be a Better Pilot

Post by boogs82 »

Hey BPF,

I've recently started a blog (links in my signature block). I'm wondering if you'd have any issue with me using your post for one of my future blog posts? It'll be sooner than later, but I want to run it by you first.
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Schooner69A
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Re: Be a Better Pilot

Post by Schooner69A »

Came across this again due to the update. I'm stealing the initial entry and forwarding it to the Editor of our newsletter.

Good points there.


John
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Big Pistons Forever
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Re: Be a Better Pilot

Post by Big Pistons Forever »

The original post was made with the intent that the subject would be of value to the pilot community. Anyone is welcome to use it in other fora if they wish.
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boogs82
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Re: Be a Better Pilot

Post by boogs82 »

Big Pistons Forever wrote:The original post was made with the intent that the subject would be of value to the pilot community. Anyone is welcome to use it in other fora if they wish.
Hey BPF,

I've written a blog posting with some of the information and sourced you as the inspiration of it.

Here is the link if you want to have a read: https://modernpilotcanada.com/2017/05/2 ... ter-pilot/

Hopefully all is good with AvCanada for posting the link to it (there's mention of AvCanada on the blog as well).
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shimmydampner
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Re: Be a Better Pilot

Post by shimmydampner »

Small aircraft don't have SOPs... but there are many factors of airmanship which apply to light aircraft that aren't written in a checklist or POH. Also, larger aircraft have more inertia and are less likely to LOSE airspeed rapidly in a case where wind is changing rapidly (we're talking gusts, not performance reducing wind shear). They'll gain speed with a gust, but it won't decay as much when the gust stops.
The size of aircraft has nothing to do with whether or not there are SOPs to fly them by. I'm quite sure you'll find a number of PA-31 operators with SOPs. Pretty small airplane. Furthermore, I'm intrigued by this theory of inertia whereby it functions only in one direction. Maybe I should factor flat earth gravity into my calculations.
Adding extra speed to the approach does not make it safer, in many case it increases the degree of difficulty
Exactly. Thankfully there's someone here willing to dispel myths like this. Now if we could get rid of others like landing with reduced or no flaps in strong winds because it's "safer."
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CpnCrunch
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Re: Be a Better Pilot

Post by CpnCrunch »

Exactly. Thankfully there's someone here willing to dispel myths like this. Now if we could get rid of others like landing with reduced or no flaps in strong winds because it's "safer."
If you look in the POH for a 150/172/182/cherokee/archer, they all say to use minimum flap and greater airspeed for taking off and landing in strong crosswinds, to minimise drift. In the 172 there can be elevator oscillation with flap settings > 20 degrees in a slip.
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Last edited by CpnCrunch on Thu Jul 13, 2017 7:11 am, edited 1 time in total.
Chris M
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Re: Be a Better Pilot

Post by Chris M »

CpnCrunch wrote:If you look in the POH for a 150/172/182/cherokee/archer, they all say to use minimum flap and greater airspeed for taking off and landing in strong crosswinds, to minimise drift. In the 172 there can be elevator oscillation with flap settings > 20 degrees in a slip.
My '75 172 POH only says that for takeoff. For crosswind landings the recommendations are to use minimum flap required and notes that elevator oscillation may be felt in full-rudder sideslip with flaps more than 20 degrees, but that this doesn't affect aircraft control. There is no mention of varying speed for crosswind landings.
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CpnCrunch
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Re: Be a Better Pilot

Post by CpnCrunch »

Chris M wrote:
My '75 172 POH only says that for takeoff. For crosswind landings the recommendations are to use minimum flap required and notes that elevator oscillation may be felt in full-rudder sideslip with flaps more than 20 degrees, but that this doesn't affect aircraft control. There is no mention of varying speed for crosswind landings.
The 172 doesn't specifically mention varying speed (the Archer and Cherokee POHs do). However if you have less flap, you will be flying faster.
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shimmydampner
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Re: Be a Better Pilot

Post by shimmydampner »

Sure, by a bit, appropriate to the flap setting. If you want. In my experience with small Cessnas and other singles, max crosswinds and beyond were always easily possible with the full flap setting for a normal landing, no control issues, no elevator oscillation, and good rudder authority. As a result, my personal feeling is that if you feel that conditions are so difficult, that landing with reduced or no flap will be the difference between a safe and an unsafe approach and landing, you are in over your head and shouldn't be landing there. But I guess if it makes you feel warm and fuzzy, even if you don't know why, who am I to tell you not to do it. The REAL problem I have with this is that, while this "technique" may have a basis in the POH for certain small aircraft, it gets touted as a flying truism across the board by pilots who don't have the experience or knowledge to back it up or understand why it may or may not be a good idea or what situations it may or may not be appropriate in. Nope, their instructor told them that, so now they just accept it as gospel henceforth, justifiable or not. Let's just have everyone zorch down the pipe in their little fart carts at 80kts to feel "safe" and then be left wondering why their landings suck and why flying seems so hard.
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CpnCrunch
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Re: Be a Better Pilot

Post by CpnCrunch »

shimmydampner wrote:Sure, by a bit, appropriate to the flap setting. If you want. In my experience with small Cessnas and other singles, max crosswinds and beyond were always easily possible with the full flap setting for a normal landing, no control issues, no elevator oscillation, and good rudder authority. As a result, my personal feeling is that if you feel that conditions are so difficult, that landing with reduced or no flap will be the difference between a safe and an unsafe approach and landing, you are in over your head and shouldn't be landing there. But I guess if it makes you feel warm and fuzzy, even if you don't know why, who am I to tell you not to do it. The REAL problem I have with this is that, while this "technique" may have a basis in the POH for certain small aircraft, it gets touted as a flying truism across the board by pilots who don't have the experience or knowledge to back it up or understand why it may or may not be a good idea or what situations it may or may not be appropriate in. Nope, their instructor told them that, so now they just accept it as gospel henceforth, justifiable or not. Let's just have everyone zorch down the pipe in their little fart carts at 80kts to feel "safe" and then be left wondering why their landings suck and why flying seems so hard.
It's gusty crosswinds that are the issue, not steady crosswinds, i.e. something like 20G30. You'll just have more control and be blown about less if your airspeed is higher, and your groundspeed won't be any higher (assuming there's a decent headwind component). It's not about being unable to track down the centreline in a crosswind, or landing with excessive airspeed...if that's an issue the student should get more training. It's just about having more control over the plane and being able to make it do exactly what you want and less likely to do any damage, which seems like a good thing to me.
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Big Pistons Forever
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Re: Be a Better Pilot

Post by Big Pistons Forever »

shimmydampner wrote: Let's just have everyone zorch down the pipe in their little fart carts at 80kts to feel "safe" and then be left wondering why their landings suck and why flying seems so hard.
I generally find if you want to influence people insulting them is not very likely to convince them of anything than other than a strong desire to tune you out.

As I have said in other posts "one size fits all " pronouncement usually don't provide much insight. So saying that every landing in every kind of aircraft under every condition has to be done with full flaps, or you are doing it "wrong" is for me, an unconvincing argument

My personal experience is use of flaps should be decided by conscious choice and for light aircraft is heavily influenced by the type of flap and the experience level of the pilot. So for instance I make every landing in my Grumman AA1B with full flaps because the small simple non slotted flaps don't have a big impact on the landing. However if I am flying a Cessna C 172 with 40 degree flaps I tend to use a reduced flap setting in crosswinds.

The reason for this is that the flaps are very powerful and that to get a proper tail low landing the airspeed at touchdown must be around 50 knots. Less flaps allows the same landing attitude with a high speed which gives more aileron effectiveness, more rudder effectiveness due to reduce rudder blanking and less severe crosswind effects. I could land with full flaps but why would I want to do that when my personal experience is that reduced flap equals better landings.

For less experienced pilots my personal experience over 29 + years of instructing was that students did better with reduced flaps when conducting cross wind landings in Cessna trainers.
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shimmydampner
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Re: Be a Better Pilot

Post by shimmydampner »

Big Pistons Forever wrote:I generally find if you want to influence people insulting them is not very likely to convince them of anything than other than a strong desire to tune you out.
I'm not concerned about influencing too many people, least of all, anonymous folks on the internet, but I did not intend to insult anyone.
Big Pistons Forever wrote:As I have said in other posts "one size fits all " pronouncement usually don't provide much insight. So saying that every landing in every kind of aircraft under every condition has to be done with full flaps, or you are doing it "wrong" is for me, an unconvincing argument
I certainly never said that every landing in every aircraft under every condition MUST be, or even SHOULD be done full flap or that doing otherwise is wrong. (In fact, I can think of a fairly common operational situation in a certain aircraft type in which I usually land with take off flap.) I was just pointing out that, in my experience as it relates to the topic of gusting crosswinds, it CAN be done without compromising safety or the controllability of the types of aircraft with which I am familiar, and therefore I think it would be ignorant to suggest that doing so is improper technique.
I think you and I are actually trying to make the same point here. I am bothered by the all too common pronouncements like proper crosswind technique is to use reduced flaps and if it's gusting, come in extra fast. It's not necessarily the espoused technique that bothers me as much as the fact that usually when I hear it, it is being put forth as some sort of incontrovertible truth and I just so happen to be a non-believer in this particular dogma. Personally, I think it's little more than a false sense of security, but if a person needs some extra warm and fuzzies on approach, that's really none of my concern.
Big Pistons Forever wrote:My personal experience is use of flaps should be decided by conscious choice and for light aircraft is heavily influenced by the type of flap and the experience level of the pilot. So for instance I make every landing in my Grumman AA1B with full flaps because the small simple non slotted flaps don't have a big impact on the landing. However if I am flying a Cessna C 172 with 40 degree flaps I tend to use a reduced flap setting in crosswinds.

The reason for this is that the flaps are very powerful and that to get a proper tail low landing the airspeed at touchdown must be around 50 knots. Less flaps allows the same landing attitude with a high speed which gives more aileron effectiveness, more rudder effectiveness due to reduce rudder blanking and less severe crosswind effects. I could land with full flaps but why would I want to do that when my personal experience is that reduced flap equals better landings.

For less experienced pilots my personal experience over 29 + years of instructing was that students did better with reduced flaps when conducting cross wind landings in Cessna trainers.
See, you are making my point for me. You evidently have significant experience and know what you are talking about. You can use that experience in conjunction with your knowledge to develop an appropriate, sound, defensible technique that works for you. You are not just ignorantly regurgitating something that someone ignorantly regurgitated at you once.
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