Be a Better Pilot

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CenterOfGravity
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Re: Be a Better Pilot

#51 Post by CenterOfGravity » Sat Sep 17, 2016 8:12 pm

Chris M wrote:Excellent info, thanks for posting. I know my engine instrument scan is a bit of a weak item for me, so that's a good way to get some practise in.

One question: On approach, should priority go to maintaining attitude or airspeed? The reason I ask is that at my field we get a decent amount of wind shear. Just part of having large buildings around and a predominant crosswind. Chasing an airspeed can result in quite a lot of pitch movement, while maintaining attitude can result in some fairly sharp airspeed drops before I gain the momentum back. I try to aim for the best middle ground, accepting a +/- range in my approach speed in order to minimize the ups and downs, particularly with passengers on board.
So, Airspeed is more your priority, especially dealing with winds shear and winds.
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Zaibatsu
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Re: Be a Better Pilot

#52 Post by Zaibatsu » Sat Sep 17, 2016 8:36 pm

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.
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cgzro
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Re: Be a Better Pilot

#53 Post by cgzro » Sat Sep 17, 2016 8:51 pm

My decision to back track would depend on a number of factors that I have not seen discussed.
What terrain is like off the end of the runway, was maintenance just performed etc.
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Re: Be a Better Pilot

#54 Post by CenterOfGravity » Sat Sep 17, 2016 11:53 pm

Taxing:

- there is no one universal taxi speed. The airplane speed should be adjusted to suit the situation. Slow down for corners or tight spots, speed up on the straight parts and when crossing runways.

An aircraft should be taxing no faster than a light jog no matter if it's straight or tight spots. Just because there is a straight path doesn't mean you should go faster. It's also probably not good for the Oleo Strut. Crossing a runway or backtracking should be the only reason for moving fast on the maneuvering area.
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CenterOfGravity
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Re: Be a Better Pilot

#55 Post by CenterOfGravity » Sun Sep 18, 2016 12:01 am

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.
Not necessarily 'fly faster'. You are however right about the gust factor. If it's for example: 10G20, you want to take half the gust factor. So if your approach is 80Mph on final, When the 20 gust becomes 10, you'd increase your speed +5Mph to compensate for losing 10knots of the headwind.
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CenterOfGravity
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Re: Be a Better Pilot

#56 Post by CenterOfGravity » Sun Sep 18, 2016 12:04 am

cgzro wrote:My decision to back track would depend on a number of factors that I have not seen discussed.
What terrain is like off the end of the runway, was maintenance just performed etc.
Backtracking makes it easier if you want to save time, for example: after landing, exiting onto a taxi way will take more time as you would have to follow it all the way around and then cross the runway. If there is no aircraft on approach and there is time to backtrack it's the best way to save your time.
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CenterOfGravity
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Re: Be a Better Pilot

#57 Post by CenterOfGravity » Sun Sep 18, 2016 12:13 am

When you are landing in strong winds, your distance from final to the runway becomes shorter than in normal flying conditions. You should always be aware of the gust load factor and fly 10kts/mph below the (Va)

The headwind is slowing you down, therefore, your descent rate or glide slope becomes steeper and shorter (also depending on the degree of flaps you are using for approach)
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Big Pistons Forever
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Re: Be a Better Pilot

#58 Post by Big Pistons Forever » Sun Sep 18, 2016 8:37 am

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.

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.

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.

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.

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.
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Big Pistons Forever
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Re: Be a Better Pilot

#59 Post by Big Pistons Forever » Sun Sep 18, 2016 8:51 am

CenterOfGravity wrote:Taxing:

- there is no one universal taxi speed. The airplane speed should be adjusted to suit the situation. Slow down for corners or tight spots, speed up on the straight parts and when crossing runways.

An aircraft should be taxing no faster than a light jog no matter if it's straight or tight spots. Just because there is a straight path doesn't mean you should go faster. It's also probably not good for the Oleo Strut. Crossing a runway or backtracking should be the only reason for moving fast on the maneuvering area.
There are many things in aviation that have more than one "right answer". I would suggest the "right" taxi speed is one of them. However I have a personal dislike for one size fits all diktats such as
An aircraft should be taxing no faster than a light jog no matter if it's straight or tight spots.
Since my original post referenced the Cessna 172 we can talk about what is appropriate for that aircraft. I think there will be times that it is entirely appropriate to taxi faster than a light jog ( ie about 10 miles per hour). If for example there is no or light winds and the taxi way surface is smooth and straight a faster taxi speed is IMO perfectly fine especially if a bit of up elevator is held. If the taxi way surface is rough or the winds strong than a quite slow taxi speed should be used.

In other words the speed of the aircraft should be proactively adjusted by pilot intent to suit the conditions and what maneuvering needs to be done, not just accepting whatever taxi speed the power setting gives you or mindlessly following a taxi speed "rule"

Finally while we are on the subject of taxi speed, a personal pet peeve; riding the brakes. I see way too much of this. If the aircraft is gong to fast reduce power if that doesn't achieve the desired result than use light braking until the desired speed is achieved. If you find that you repeatedly having to use brake to slow then you have set the taxi power RPM too high.
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Zaibatsu
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Re: Be a Better Pilot

#60 Post by Zaibatsu » Sun Sep 18, 2016 9:49 am

CenterOfGravity 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.
Not necessarily 'fly faster'. You are however right about the gust factor. If it's for example: 10G20, you want to take half the gust factor. So if your approach is 80Mph on final, When the 20 gust becomes 10, you'd increase your speed +5Mph to compensate for losing 10knots of the headwind.
That sounds like flying faster. :wink:
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Re: Be a Better Pilot

#61 Post by Zaibatsu » Sun Sep 18, 2016 10:08 am

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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Re: Be a Better Pilot

#62 Post by trampbike » Sun Sep 18, 2016 8:45 pm

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

#63 Post by Zaibatsu » Mon Sep 19, 2016 8:12 am

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

#64 Post by Big Pistons Forever » Tue Sep 27, 2016 6:32 pm

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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Re: Be a Better Pilot

#65 Post by Gannet167 » Wed Sep 28, 2016 9:46 am

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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Re: Be a Better Pilot

#66 Post by fixedpitch » Wed Sep 28, 2016 10:34 am

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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Re: Be a Better Pilot

#67 Post by Big Pistons Forever » Sat Oct 01, 2016 3:33 pm

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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Re: Be a Better Pilot

#68 Post by waterdog » Mon May 22, 2017 7:41 pm

BPF

New pilot, awesome original post.

Thanks for posting!
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Re: Be a Better Pilot

#69 Post by boogs82 » Mon May 22, 2017 8:51 pm

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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Re: Be a Better Pilot

#70 Post by Schooner69A » Tue May 23, 2017 7:36 am

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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Re: Be a Better Pilot

#71 Post by Big Pistons Forever » Wed May 24, 2017 7:08 am

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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Re: Be a Better Pilot

#72 Post by boogs82 » Fri May 26, 2017 9:01 pm

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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Re: Be a Better Pilot

#73 Post by shimmydampner » Wed Jul 12, 2017 7:10 pm

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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Re: Be a Better Pilot

#74 Post by CpnCrunch » Wed Jul 12, 2017 9:07 pm

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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Chris M
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Re: Be a Better Pilot

#75 Post by Chris M » Thu Jul 13, 2017 6:24 am

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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