The Hangar

falstro

03:17

First flight a) downunder, and b) with an SR20 in the books. Yeeey! :)

Shalvenay

@falstro nice!

falstro

And first flight with glass cockpit to boot

I think @BretCopeland flies the SR20 (22?) on a regular basis. Lucky bastard... ;)

Shalvenay

I just hope someone here can unravel the mystery (in my eyes) that is the lack of sidestep ILS approaches at Gatwick

Bret Copeland

I don't always fly airplanes, but when I do, I prefer the SR20.

Shalvenay

@BretCopeland heheh

Bret Copeland

03:25

@falstro nice. Happy in the southern hemisphere?

falstro

@BretCopeland takes a while to get used to the fact that the sun is to the north... and it's hot as hell :P

unfortunately not here permanently as of yet though, going back to europe in a couple of weeks.

... and they have funny phraseology down here :)

Bret Copeland

examples?

falstro

"maintain 1500, join the downwind" does not mean you can fly your base and final, but you have to stay at 1500 until you get "cleared for the visual approach" (which, to me, is an IFR clearance rather than a VFR one)

also taxi clearances have crossing instructions inline rather than at the end

they have a "gliding approach" which I've never heard before, don't know if it's used in FAA land (simulated engine failure)

and "join the downwind for 10R" does not mean a left downwind, it means a right downwind. (since the ERSA, the A/FD equivalent, lists the normal pattern for 10R as right pattern they don't need to tell you)

at least, that's what I gather, could be that it's implied through 10R having right pattern and 10L having a left pattern.

Bret Copeland

huh, that's all just a little bit odd.

being cleared for a visual approach is definitely an IFR thing in the US.

Not sure about gliding approach. We say "short approach" sometimes when ATC wants you to make a tight turn from downwind to final. It basically amounts to cutting power abeam the numbers and turning 180°.

falstro

03:42

nope, this means starting at 2000agl and chopping power over the field or on the downwind

and yeah, it's not assigned by atc, it's requested by the pilot

Dan Hulme

08:30

oh, like a practice forced landing

user183836

15:38

anyone think they can feel ground effect?

ratchet freak

15:53

I've heard it described as a cushion of air right before touchdown

Jay Carr

16:11

@Dawn "Think" or "actually can". I know plenty of people who think they can feel any number of phenomena they can't actually feel...

ratchet freak

just listen to an audiophile "hear" imperfections in your audio setup

Jay Carr

16:40

@ratchetfreak Well, as someone who has worked in a studio before I do feel obligated to point out that some of the more talented Masterer's out there can actually do this but...yeah, most audiophiles are just a lot of hubris.

user183836

16:54

@JayCarr ya that's what I was trying to get to in this comment thread aviation.stackexchange.com/a/25764/13148

user183836

Not a big deal, but I don't trust that I actually feel ground effect.

voretaq7

17:05

@Dawn Yup: Every time I do a short-field takeoff.

You will know immediately upon leaving ground effect if you do it wrong: The Cherokee will go "Fly? At this airspeed? HAHAHAHAHAHAHA NOPE!"

Jay Carr

17:17

@voretaq7 Do you feel the ground effect though, or do you just feel the stall when you leave ground effect and your plane doesn't want to do it.

I mean, does ground effect feel any different than normal lift?

voretaq7

@JayCarr "what's the difference?" :)

Jay Carr

@voretaq7 Yes, I do in fact believe that is the question I'm asking.

Or rather, if there is one.

I've never felt it, but my experience is pretty limited.

voretaq7

Well like dave mentioned you'll feel it if you intentionally fly a few feet over the runway

user183836

I've felt what some people might call a "cushion of air" prior to landing, but until now, I've always done an intentional round out and hold off, so was that "cushion of air" just caused by my own control inputs?

voretaq7

@Dawn a little from column A, a little from column B I suspect

user183836

17:21

@voretaq7 He claims that you feel it, but in my experience, I've never felt anything that I could definitively assign to ground effect

user183836

Flying in straight and level flight 10ft above a flat surface... how does that feel different than flying in straight and level flight at 1000 ft?

user183836

There will be more turbulence

voretaq7

I know in the Cherokee if you keep power in like for a soft-field landing & descend effectively in a level-flight attitude you'll reach a point (about 10 feet off the runway) where your sink rate gets close to zero

user183836

3d will be enhanced

user183836

@voretaq7 Without changing your attitude whatso-ever?

user183836

17:23

I've had somebody try to show me this, but invariably, they do move the control column aft

voretaq7

@Dawn keeping the pitch the same (you might be moving the controls, but the horizon stays where it is)

user183836

that is not possible

voretaq7

you just sort of float along until your take the power away (and at that point yes, you flare - otherwise you're landing either flat or on the nose)

user183836

unless your decent wasn't actually stabilized

user183836

i don't know how to reconcile that with my experience

user183836

17:26

have i misremembered>

user183836

?

voretaq7

@Dawn I would say it's not possible if I hadn't seen (and been made to do) it - it's not an "oh my god wow" feeling, but there's a change in the aircraft's behavior

user183836

what kind of decent rate did you establish on approach? Like 100 ft / min decent? And you're saying without changing flight attitude, entry into ground effect on its own reduces that decent rate to something like 10 ft / min?

user183836

of course there's a change in the aircraft's behaviour... i'm doubting that it is of a magnitude that is "feel"-able, and proposing that anything that you do "feel" is due to factors other than ground effect

voretaq7

@Dawn we went from about 50ft/min to around 10 - it was definitely not anything like a normal approach to landing

user183836

17:29

okay, so you're saying ground effect changed the rate of decent by 40 ft / min without any change in aircraft attitude

voretaq7

@Dawn I guess it depends what you mean by "feel" - it's not Bigby's Hand suddenly cupping your airplane and pushing it away from the ground, but it is a noticeable change in the way the aircraft behaves.

user183836

wing span is 30 feet, so decending at 50 ft / min, if ground efffect wasn't present, you'd close the gap between 30 feet and ground in a time of 36 seconds

user183836

but instead, before you hit the ground in those 36 seconds, ground effect intervened and slowed your decent

Jay Carr

It feels like you are arguing that ground effect doesn't exist? And thus can't slow someone down?

user183836

no not at all

user183836

17:32

ground effect absolutely exists

user183836

i'm doubting that it is of a magnitude that is "feel"-able, and I'm proposing an alternative that anything that you do "feel" is due to factors other than ground effect

voretaq7

@Dawn by an amount I could notice on the instruments, yes. Was some of that 50 feet instrumentation error? Sure, it's possible. The static source is right under the wing on the Cherokee

Jay Carr

@voretaq7 So this is instrument readings, not "seat of the pants"?

Because that's the real question here. If you can feel it.

voretaq7

@JayCarr The descent rate observation is based on my instructor flying the plane and telling me to watch the attitude and the descent rate

user183836

ideally, we'd set an aircraft up in a stable, very shallow decent, in still air, with no low level convection, let it come down into ground effect, and see if Gs increase above 1G

user183836

17:35

@voretaq7 so you don't actually know if the instructor input subtle control inputs

voretaq7

@Dawn Nope, the plane is not instrumented with laser micrometers on the control yokes.

user183836

i say we'd need no low level convection because runways typically heat up and there is some convection there too

Jay Carr

@Dawn I don't think you'd need 1G in order to feel it, though that does make me wonder what the minimum amount of impulse force is to be felt...

voretaq7

@Dawn you'd need an absolutely static test chamber with no airflow other than what's caused by the wing

Jay Carr

Oh, wait, I'm stupid.

user183836

17:36

@JayCarr Well i'm assuming 1G is what you feel in the stable decent

voretaq7

because otherwise some control input is going to be required and you can't rule it out as a "cause"

Jay Carr

Sorry, you meant if Gs increase above the 1G you already feel, right.

user183836

yup :)

Jay Carr

I was thinking in terms of added Gees :)

user183836

Geeees

Jay Carr

17:37

I'm with @voretaq7 though, I think testing this would be awful hard because you'd need a very controlled enviroment to figure it out. Or maybe just some very good math...

user183836

but, as I said when I started, this isn't a huge deal. It does seem like it was useful as an instructional point for you, though

user183836

maybe in as much as it made you aware of how the ground and things look around you as you approach the runway

voretaq7

@JayCarr yeah, and the effect would be very subtle if that: I've never felt ground effect "in the seat of my pants" personally. I've felt the aerodynamic effects as a change in control forces or aircraft performance, but there are a lot of other things that can cause those sensations too

@Dawn "Big." :-)

user183836

and fast :)

voretaq7

@Dawn "It's only a 5 knot tailwind, we're not changing the runway!"

user183836

17:45

my alternative theory is this: the effects of small control inputs are more apparent when you're close to the ground. ballooning from 5 ft to 10 ft is super apparent. "ballooning" from 1005 ft to 1010 ft is not noticeable at all. this extra awareness is more of a factor than ground effect in how we "feel" close to the ground

voretaq7

@Dawn There's definitely a psychological difference flying close to something (other aircraft, the ground) - there's no way to deny that.

egid

18:06

@voretaq7 vsi has a lag, don't forget

that said, i would be pretty surprised if ground effect is intangible

we need to get Peter Kämpf in here

also, the 'cushion of air' explanation doesn't make any sense if you think about how GE works

you're not gaining lift, you're feeling a reduction in drag

user183836

it does change the induced angle of attack

voretaq7

@egid yeah, and on the Piper it gets "perturbed" on the ground with any wind gusts (±5ft/min)

user183836

which tips the aerodynamic force vector a bit more upright... i guess reducing drag and increasing lift

egid

so my point though

is that the 'cushion' is the wrong analogy

user183836

but it's not cause of a "cushion"; that change in how the air is turning around the wing is because of stuff happening kind of behind the aircraft

user183836

18:12

ya. agreed

egid

it's more like you suddenly gained 50hp

well

n hp

5, perhaps

user183836

da-20s are 80hp

user183836

lol

egid

heh

yes

user183836

it's all relative i guess

egid

18:13

anyhoo in cruise, the most immediate simulation you could probably do

is to add 50rpm or something after you are established in level flight

that is what ground effect is basically doing at a practical level - right?

it's causing an imbalance to the thrust/drag ratio after you are already stabilized

user183836

x rpm. yeah

egid

in theory

so i would argue that it's absolutely going to be tangible

source: i taught a lot of people to land

user183836

of course it's tangible, if you mean measurable

egid

that's measurable. i mean tangible - you the pilot can feel the effect

perceptible

user183836

how do you rule out the possibility that everything you're feeling down near the runway is due to things other than ground effect

user183836

18:15

and that while ground effect is a part of it, it is masked by the other factors

user183836

i've also taught a lot of people how to land, so we're tied :P

egid

i mean i guess from a perception standpoint you can't

but from a science standpoint i feel like you can

we know the effect it has on an aircraft

user183836

yes

egid

it is a non-zero contribution to how an airplane behaves while landing

user183836

yup

user183836

18:18

but whether the "floating feeling" you get is due largely to ground effect is not established, as far as I can tell

egid

wellllll okay now i'm not sure anyone said the float is 100% ground effect

or even largely

user183836

noone said that

user183836

people do say largely

egid

well

they're probably landing too fast

:)

speed is going to directly impact GE, fwiw

so a carbon cub landing in 50' is going to have a lot less energy getting fed into ground effect than an SR22T that is 15 knots fast over the numbers

voretaq7

18:39

@egid This. If you're "feeling" a float in the seat of your pants it's probably your poor airspeed control more than "ground effect" doing it.

egid

i'm not so much thinking seat of the pants

but that you're responding to the effects with controls

voretaq7

@egid that gets into the sticky questions of what you can "feel" versus what can be objectively measured though: A lot of what we "feel" is psychological as much as physiological.

egid

shrug.gif

voretaq7

Can I detect a difference in how aileron control affects the Cherokee on a soft-field takeoff? Sure. How much of that is from the aerodynamic impact of accelerating in ground effect versus "I'm 3 feet off the bloody ground - everything looks so big!" -- I couldn't tell you :)

voretaq7

19:15

Dear god Cessna flight manuals are actively hostile to pilots, aren't they?

Jay Carr

20:40

@voretaq7 Example?

voretaq7

@JayCarr That table - really?

Jay Carr

Wow, I think my gui designer would flip his lid.

voretaq7

I know the Piper charts aren't going to win any usability awards either (you mean I have to figure my density altitude before I can use the chart?!), but still... ugh!

falstro

21:28

@voretaq7 looks pretty standard to me?

voretaq7

@falstro I object to having to make calculations to find my true airspeed (indicated altitude to pressure altitude, pressure altitude to density altitude (interpolating based on the 3 temperature points given).

actually to be honest I object to doing any kind of math whatsoever. I WAS TOLD THERE WOULD BE NO MATH! :)

user183836

user183836

Diamond just has you follow lines up and across until they intersect other lines

falstro

@Dawn looks like the Katana POH

voretaq7

Piper pilots are lazy. Point at altitude, follow line to throttle setting. Read number. Write off any error as "the chart is blurry anyway" :P)

falstro

21:31

ah right

voretaq7

@Dawn Apparently Katana pilots are lazy too :-)

user183836

Ya it's DA20-100 HP version

falstro

Cirrus has the same kind of tables as Cessna does

(only temperatures are listed as absolute, not relative to standard)

voretaq7

@falstro I would actually prefer the Cessna table if it listed like 5 absolute temperatures

"Standard -20, Standard, Standard +20" is a punt: You figure it out, we didn't want to make the chart by density altitude or make it take 2 pages with more temperatures.

falstro

actually nevermind, the power settings are ISA ± 30 :)

takeoff/landing distances are with temperatures

but with the ADC in the Cirrus, you just set the percentage anyway... no math required ;)

Dan Hulme

21:53

at least you guys get a POH

there was a POH for the Tiger Moth once, but no longer

voretaq7

22:03

@DanHulme I get an AFM and an "owner's manual"

The AFM basically says "It's an airplane. The stall warning is electric. Here's the CG operating envelope."

The "owner's manual" is a delightful work of fiction, no parts of which are FAA approved :P

falstro

What I don't like about the stall warning in the Cirrus is that a) it's electric and b) it doesn't work if the avionics are off.

voretaq7

@falstro Do you really need a horn or light to tell you the plane is handling like shit and doesn't want to fly the way you're making it though? :)

falstro

@voretaq7 that's fine for straight-and-level stalls, the accelerated ones are less obvious, in my opinion.

Although the "Stall, stall" voice is kinda cool... ;)

voretaq7

@falstro I know the Cherokee still shakes.

"I AM NOT HAPPY!"
What did I do?!
"YOU KNOW WHAT YOU DID PILOT!"

(not to be confused with the Airbus stall warning where a little door next to the stick opens up and a mechanical hand comes out to smack you with a newspaper while the voice says "NON!")

4

falstro

Dunno, the cirrus shakes (rather violently I might add, compared to the Katana which has otherwise similar stall characteristics) right as it's about to stall, don't want to get that close in a steep turn... (the only certified spin-recovery in the cirrus is the chute)

voretaq7

22:14

Passive stall warning device: The buffet/shake
Aggressive stall warning device: Horn, Light, or the voice saying "Stall. Stall."
Passive-Aggressive stall warning device: "No, it's cool. You just keep pulling back on that stick like I've got infinite energy. I'm sure *nothing bad will happen*."

@falstro I thought that was item #3 on the Cirrus landing checklist?

falstro

:D

heh

it IS actually the #3

on the ditching checklist

voretaq7

oh this reminds me (since we're talking about things that are usually safetied, like the big red handle) I need to replace the safety wire on my fire extinguisher.

falstro

I was surprised to learn the chute activation handle requires ~45lbs of force to pull

voretaq7

@falstro well it's not something you want a passenger accidentally activating :)

and 45lbs isn't a lot of force when you think about it

falstro

it's in the ceiling though so you can pretty much pull yourself up using the handle, and it'll activate

45lbs is a lot when your arms dont have their full range of motion

voretaq7

22:18

@falstro yup. And you should really make sure your passengers know not to do that :-)

I'm surprised Cirrus didn't make it a two-stage handle (twist & pull)

falstro

it's three stage

remove cover, pull the handle downwards (i.e. twist it), then pull.

on the WT9 it's just pull, and it takes a lot less force (can't remember how much though)

voretaq7

@falstro Yeah I guess the cover counts as a stage, the "pull handle downwards" is just part of the pull though isn't it?

you don't have to go through a separate stage to unlock it (provided you took the pin out like you're supposed to)

falstro

you probably could, but it's pretty flush so you'd probably have to change your grip to get the full 45lbs force on it

the POH calls for removing the pin during preflight, which I find absolutely ludicrious

voretaq7

@falstro that's sensible: you close the access panel again so you have to open it to get to the handle

on other planes (the CTLS springs to mind) the handle is just "out there" right with the other controls, you pull the pin and any idiot can yank the handle now, at least in the Cirrus it's out of the way

falstro

yes, and I suppose that'll protect it enough, but I still don't want a live rocket-launching-handle around when I'm mucking about in the cabin... :P

voretaq7

22:26

yeah but you also don't want to be trying to pull the pin from the pilot's seat in an emergency, it's not the easiest spot to reach as you mentioned :-)

falstro

@voretaq7 yeah, it's the same in the WT9

@voretaq7 yes, that's why you pull the pin before engine start

when everybody is strapped in

voretaq7

Personally if I were designing it I'd safety it with copper break-away wire or something - enough to keep it from accidentally activating, but easy to break when you really want to pull the fucking thing

or I'd make it a two-stage handle (twist 90 degrees and pull, or push in & pull down like fire alarm handles)

falstro

I just think say kids heading into the back seat a little too quickly, catching the handle with their backpack or something and pulls on it without thinking.

voretaq7

@falstro yeah, that would be difficult to explain to your insurance adjuster :)

I don't have these problems, I have an airplane that expects you to fly it to the scene of the crash.

falstro

especially if you're still in the hangar... leaves a nice rocket-shaped hole in the roof.

voretaq7

22:29

But it's made of metal! :-)

falstro

:)

voretaq7

(speaking of metal, the poor mooney next to me seems to have been hit by a something and I still wanna know what!)

falstro

yeah, I usually fly the Tb10 nowadays, it's also mostly metal ;)

yeah you mentioned; still no idea what happened?

voretaq7

Nope, the line guy I talked to when I brought my plane over to the shop said he didn't know either, one day it was fine, the next... crunch

(happy it wasn't me getting crunched, but I really wanna know what happened!)

falstro

Wow. The CASA password requirements are ridiculous.

Dan Hulme

22:37

stall warnings, pah

falstro

> The password must contain at least 10 characters.
> The password must contain at least one numeric character [0-9].
> The password must contain at least one upper-case alphabetic character.
> The password must contain at least one special character from this set: [! $ & % ? , - _ # § £].
> The password must contain at least one lower-case alphabetic character.
> The password must not contain any utf-8 characters.

voretaq7

@falstro . . . so much for making your password an endless series of the Poop emoji.

falstro

and, / is not one of the special characters...

neither is +

Dan Hulme

no utf-8 characters?

voretaq7

@falstro you're allowed to use % so there's that.

Dan Hulme

22:40

that excludes all of ASCII then

voretaq7

@DanHulme Shh.

falstro

@voretaq7 oh you are allowed to use / and +, they just don't count towards the 'use one of the special characters' goal :P

voretaq7

and it doesn't exclude ALL of ASCII - you can make your password formfeed vertical tab linefeed linefeed end-of-text :)

falstro

@voretaq7 but yeah.. ' OR 1==1; -- here we go... ;)

voretaq7

I'm not quite sure how you would go about TYPING that password, but it would be VERY secure! :)

falstro

22:50

actually, turns out you can't use any special characters which aren't in the set :P

Transcript for