What would you do?

[Colonel Sanders]

Doomsday scenario: You screwed the pooch.

You are IFR in a piston aircraft in the clear on
top, approaching your destination airport with
a layer of "moderate" icing extending from 6000
to 200. Airport is at sea level.

You don't have enough fuel to fly someplace
that doesn't have the "moderate" icing layer,
so you've got to fly the ILS to your destination.

Now, ATC is going to want you to descend early
and make you fly for a long time in nasty icing
conditions (see Rosedale, Indiana) but you refuse,
because you want to fly in the icing conditions
for the shortest time possible (hint, hint)

Here's another hint: a 3 degree glideslope is
300 feet for every nautical mile.

What are you going to tell ATC that you're going
to do?

[photofly]

3° is 318 feet per NM.

Pick up the ILS 18.849 miles out and fly it nice and fast. Flapless landing. An ILS-equipped runway is easily going to be long enough for a fast approach in a piston single.

Isn't the official range of the localizer 18.00 NM within 10.0°?

[Rookie50]

Doomsday scenario: You screwed the pooch.

You are IFR in a piston aircraft in the clear on
top, approaching your destination airport with
a layer of "moderate" icing extending from 6000
to 200. Airport is at sea level.

You don't have enough fuel to fly someplace
that doesn't have the "moderate" icing layer,
so you've got to fly the ILS to your destination.

Now, ATC is going to want you to descend early
and make you fly for a long time in nasty icing
conditions (see Rosedale, Indiana) but you refuse,
because you want to fly in the icing conditions
for the shortest time possible (hint, hint)

Here's another hint: a 3 degree glideslope is
300 feet for every nautical mile.

What are you going to tell ATC that you're going
to do?

I would tell them -- I'll do a slam dunk approach, start the descent at the FAF, say 6 nm, 120 indicated, 2000+ Fpm down. 3 minutes and you are there. Seems like safest option. Keep the speed up on landing, too.

[photofly]

One turn in a shuttle descent at the FAF at 1500fpm, then pick up the g/s at 120kts?

[Skyhunter]

I don't fly a light piston twin. Did 25 hours in one 25ish years ago. But I will take a shot at what I would do.
Assumptions... for ease of explanation,, plan could be adjusted slightly for variables.
Sea level field elavation
calm wind (reasonable for most freezing rain/icing conditions)
FAF 1500' agl
ATC agrees with my request (note if push comes to shove it would be an advisory not a request)

Fly a hold at the FAF inbound on the loc. Just above the ice.
over the fix on entry or if required after first turn in hold, dirty the airplane, props fine, gear down, flaps as recommended by the manufacturer for that type, etc. Hold the alt.

Abeam fix outbound throttles idle and speed that makes sense for the type. Probably just a couple knots below the limiting speed of gear or flaps.

Note the rate of decent. (for this problem assume it is 2500 fpm) this will be alt I will lose in rate one turn to be inbound.
Subtract rate of descent from from 4500' and divide by 2 (top of ice - FAF) in this case 4500-2500 = 2000, divide by two = 1000.
when I get to 5000 turn inbound with a rate one turn (6000-1000 from above math)
I will be at 2500' at end of turn inbound.
I will cross the FAF at 1500' and intercepting Glide Path.

Finish the approach and at minimums slower up and land.

Came up with that plan in about 2 minutes. Others would probably come up with own that would work better of course. Adjustments could be made for wind and different field altitudes as required and different actual rates of decent. Pretty easy math to do in your head.

Feel free to point out the errors in this plan as this is far from my area of expertise.

[digits_]

Fly a holding-like pattern over the FAF (increasing/decreasing the legs depending on your altitude), engines on a low power setting and red line the speed, assuming there is no turbulence. Once on the ILS you slow down to a more conventional speed, until you are at your usual speed (+ a few knots for possible icing) at 500 ft or so.

[B52]

First, it sounds like it is a no go-around approach, so
the minimum time on the descent, plan the descent point
based on known performance, and your ability.
Request the latest possible descent point, straight in high speed.

Power back to idle, props fine, clean, High speed descent
say 6,000 down to 2,200, guess, 180 kts for about 8 miles from the FAF,
transition from high speed clean to gear down clean landing.
Keep the speed up to max gear extension speed until short final.

Others may vary but I'd keep the gear and flaps up until short final.

No holding pattern.

Make sure you have practiced high speed ISL approaches
down to the ground which should be part of challenging training
because it may be below minimums.

[Richard_K_Spyte]

Descend late and capture GS from above.

[mdh]

Easy, pull the BRS.

[fish4life]

However you want to do it keep one thing in mind if you pooch the approach trying to minimize your time in icing you will be way more screwed if you have to try go around.

[ReserveTank]

1500 FPM descent to FAF from 6000' On the Localizer...GS doesn't matter at this point. That's 3 minutes to FAF. 6 NM if you are configured for 120 KT. Once at the FAF, fly the GS 1 dot low. Break out, finish landing config. Runway's in sight and you won't overrun.
4-5 minutes tops to get on the ground...all without holds or unreasonable airspeed.

[Pratt X 3]

[mike123]

Not instrument rated, but will give it a shot.
I would be 18 nm away from the threshold if I intercept the glide path at 6000'. Fly further 13 nm, climb to 7500', then descending rate 1 turn at 1500 fpm, 4 min later I am 5 nm away from the threshold at 1500', inbound. Intercept the glide path, slow down to a safe speed.

[Meddler]

I would try to avoid doing too much math or fancy flying since Id be stressed right out. And if I screw it up all the folks on avcanada will wag their fingers at my corpse.

I would just set up for a straight in, high speed ils, clean, staying on top till the glide slope is intercepted. Leave gear till late, and flaps up.

Ask for pireps, mb its not full on moderate for the whole 6000'. Actually it almost certainly wouldn't be.

Double check all the de ice stuff is on and working. We have de ice stuff.....right?

[Colonel Sanders]

staying on top till the glide slope is intercepted

At what altitude? Specifically, what distance
would you tell ATC that you want to intercept
the LOC?

PS There are two advantages to flying the ILS fast, if
you can keep the needles in the donuts. Obviously you
spend less time in the icing, but what's the other?

Calculate it for Vne of 200 knots (gear and flaps up,
all the levers forward)

[Meddler]

Somebody else already calculated it. Just over 18 miles back would give you GS intercept just above the clouds.

There are lots of advantages to flying it fast. Burn less gas, save that big .1 airtime in the logbook, get to the bar quicker......but I imagine your're thinking that by staying fast you'll avoid getting ice on parts of the plane that are more exposed at slow speed, and unprotected.

[Meddler]

Plus you're farther above the stall speed if you do ice up.

The downside of course is that flying an ils that fast is it makes it a lot easier to screw up, and unless you've practiced lots of 200kt ils s, you"ll probably screw it up. Breaking out at minimums in half mile or less with ice on the windshield and landing in the right spot is challenging enough for most of us at ref, let alone if your going ref plus fifty.

Maybe we should also discuss planning including weather, possible delays, headwinds, etc to avoid the challeges of these heroic aproaches?

[spaner]

nope, and it exhausts me, just to state such...

man it's so simple, that I do it all the time, just for FUN...FOR FUN...

If you can't, than what's the point, WHAT IS THE POINT?

I bring it in at break neck speed, just to see if I can, if I could. and I did...now what?

Calculate what?

The 3-6-9...12...15? @250, maybe...

@200 sometimes? Who's watching anyway?

The colonel (Col)?

Vivaldi, such is the consideration...

http://www.youtube.com/watch?v=KdCAfK_CN8U

[digits_]

Burn less gas

That's not true. You'll burn the least gas somewhere around best glide speed (drag small), not around Vne (drag huge).

[spaner]

POST, yes please, ha, ha,

Such is the way that knowledge is passed,

Ever hear of "time-to-touch-down"...

Depends on a lot of factors, for sure.. The one that can not be disputed, is "Total-fuel-burn" @touch-down" via the FADEC...

The fuel burned to get there, no matter how you decided to do that.

Vne or Best-Drag, really depends on where the pwr levers are, at what point in time.
If you come in on the back side of the pwr curve, and then pwr to final, or,
Come in hot, and pwr down and throw out the junk, just to get it all under control,

There is a balance in there somewhere, no matter what the type.
No matter what the FCU....
No matter what the FADEC...

Time vs Burn vs Envelope...

It's a type designed perfection, when executed properly,
And, when not, I beat your type, every time...

Just for fun, for FUN...


http://www.youtube.com/watch?v=nGdFHJXciAQ

[Colonel Sanders]

Maybe we should also discuss planning

Good point, but this is the internet, where thread drift
has never, ever occurred before, and never will.

First sentence of the thread:

Doomsday scenario: You screwed the pooch.

What I would do (merely my opinion - there are other
good answers as well):

I would get some speed up (throttle and prop all
the way forward, mixture leaned for best airspeed,
gear and flap up) and tell ATC I want vectors to
intercept the LOC at 7k at 25 miles (!) out, and
leave all the knobs in for max level speed, and
intercept the GS at 21 miles at 7k on the LOC,
and dive for more airspeed on the GS by the time
I entered the icing in cloud at 6k at 18 miles out.

Gear up, flaps up, all the knobs in for max airspeed
on the GS until I was visual, then gear, no flap
(remember tail icing).

Keep the speed up to Vs x 1.5 until I was a foot over
the runway. No flaps until I was a foot over the runway.

[Colonel Sanders]

The above is sure to upset the four-bars. Let's
look at another option which won't make them
any more happy

The above high speed ILS requires that you spend
6 minutes in "moderate" icing, using a rough number
of 3 nm/min and entering cloud at 6000 on the GS
at 18 miles back.

That's a long, long time to spend in "moderate" icing.
If that doesn't make you pucker, I don't what will.

Utilizing on of the steep, false GS is a fascinating
option. Let's take it to the extreme.

Let's say I'm stuck on top of the 6000 foot icing
layer in the Pitts or aerobatic monoplane. I know,
I know, poor planning.

But it's interesting to think about the options.

Here's one: Climb to 8000 feet, just short of the
runway threshold. Nice and slow at the apogee,
1/2 roll inverted and pull gently to the vertical
downline. Alt air selected, and set power for Vne
plus a little bit (see Vd).

Ride the prop down vertically, using the throttle to
hold the airspeed at Vne + 10%. This works best
with the cloud at 500 feet, actually. As soon as
you are visual, pull level and hope that you don't
stall either the wing or the tail, which is the tricky bit.

This sounds insane (because it is), but it would get
you vertically through the icing layer in under a minute,
compared to the hairy harrumphing high-speed ILS
which takes SIX minutes in "moderate" icing.

[cdnpilot77]

This sounds insane (because it is), but it would get
you vertically through the icing layer in under a minute,
compared to the hairy harrumphing high-speed ILS
which takes SIX minutes in "moderate" icing.

Lol, are you obligated to say "watch this" over the radio first?

[davecessna]

Easy, pull the BRS.

Amen, Reverend.

[digits_]

Gear up, flaps up, all the knobs in for max airspeed
on the GS until I was visual, then gear, no flap
(remember tail icing).

Keep the speed up to Vs x 1.5 until I was a foot over
the runway. No flaps until I was a foot over the runway.

Max airspeed and no gear until 200 ft agl ? Wouldn't that require a freakishly long runway ? You are at high speed, so you need to slow down without any help from gear or flaps, since you'll be most probably be above their limiting speeds. Would you be able to slow down enough (let's say from 200 kts Vne to 80 knots) in the first half of a 10 000 ft runway ?

Honest question, never tried this in reality. I have a feeling you've tried it before