Approach speeds for ILS

"C J Campbell" wrote in message
...

you are not going to slow from 90 knots to 60 in a Skyhawk in only 200
feet
of altitude, especially if you can't risk ballooning back up into the
soup.

What speed do you use to fly the ILS if asked to "keep your speed up"?

ILS runways are usually 5,000 feet or longer. You could dissipate speed
over the runway.

I suspect if you cross the runway threshold right on the glideslope at 90
knots in a Skyhawk with a 5,000 foot runway, there is no way you could
overrun the runway if you tried.

--
Richard Kaplan, CFII

www.flyimc.com

"Richard Kaplan" wrote
What speed do you use to fly the ILS if asked to "keep your speed up"?

These are different situations. If you're asked to keep your speed
up, it's generally because you're landing at an air carrier airport.
That means only minimal tailwinds (if any) and very long runways. You
can float and float and float and land 5000+ ft down the runway and
it's still fine. Being able to fly an ILS fast is an important skill,
but it's not the ONLY important skill.

ILS runways are usually 5,000 feet or longer. You could dissipate speed
over the runway.

It's true that ILS runways with a total length of less than 5000 ft
are pretty rare - at least I've never seen one. However, the ILS and
(typically available) visual glideslope aid will not put you on the
numbers. Having an available landing distance of less than 5000 ft is
actually pretty common. Unfortunately, this typically happens at
airports served by only one ILS. If the weather is low enough to need
an ILS, it may require a tailwind landing. At such a place you will
not be asked to keep your speed up (unless the controller really
screwed up). On the other hand, if you're a bit fast on the ILS and a
bit slow to retard the throttle, you do risk overrunning the runway.

This brings us to another interesting problem. When visibilities are
less than a mile, especially at night, the visual cues available are
not really sufficient for precise control of the airplane. The visual
segment must be flown with at least some reference to instruments.
This is not something that is normally taught, and it's not really
something you can effectively practice in blue sky conditions. I
suspect that most of the pilots having trouble slowing down would have
done fine in good VMC flying under the hood.

I personally like to take an advanced instrument student to an airport
served by only one ILS when that approach is downwind, preferably in
low vis, at night, or both. This quickly reveals any lingering
technique issues, and lets us work them out in an environment that
won't cover them up. Once he can handle landing out of an ILS at
night with a 10 kt tailwind, he can pretty much handle any straight in
visual segment.

I suspect if you cross the runway threshold right on the glideslope at 90
knots in a Skyhawk with a 5,000 foot runway, there is no way you could
overrun the runway if you tried.

I suspect you're right - as long as there is really 5000 ft of landing
distance available and no significant tailwind. However, lately I'm
seeing a lot of people flying the ILS at 100+ kts in Cherokees and
Skyhawks. I find this fascinating since it's faster than I fly the
ILS in my twin, unless I am specifically instructed to keep my speed
up.

Michael

chino california (CNO) the ILS on 26R is 4858 ft.
my wife took pictures all the way down the glideslope a few months ago, there
was no clouds that day, just some ground fog.
http://www.turboarrow3.com/newplane/chino/index.html



Michael wrote:

"Richard Kaplan" wrote
What speed do you use to fly the ILS if asked to "keep your speed up"?

These are different situations. If you're asked to keep your speed
up, it's generally because you're landing at an air carrier airport.
That means only minimal tailwinds (if any) and very long runways. You
can float and float and float and land 5000+ ft down the runway and
it's still fine. Being able to fly an ILS fast is an important skill,
but it's not the ONLY important skill.

ILS runways are usually 5,000 feet or longer. You could dissipate speed
over the runway.

It's true that ILS runways with a total length of less than 5000 ft
are pretty rare - at least I've never seen one. However, the ILS and
(typically available) visual glideslope aid will not put you on the
numbers. Having an available landing distance of less than 5000 ft is
actually pretty common. Unfortunately, this typically happens at
airports served by only one ILS. If the weather is low enough to need
an ILS, it may require a tailwind landing. At such a place you will
not be asked to keep your speed up (unless the controller really
screwed up). On the other hand, if you're a bit fast on the ILS and a
bit slow to retard the throttle, you do risk overrunning the runway.

This brings us to another interesting problem. When visibilities are
less than a mile, especially at night, the visual cues available are
not really sufficient for precise control of the airplane. The visual
segment must be flown with at least some reference to instruments.
This is not something that is normally taught, and it's not really
something you can effectively practice in blue sky conditions. I
suspect that most of the pilots having trouble slowing down would have
done fine in good VMC flying under the hood.

I personally like to take an advanced instrument student to an airport
served by only one ILS when that approach is downwind, preferably in
low vis, at night, or both. This quickly reveals any lingering
technique issues, and lets us work them out in an environment that
won't cover them up. Once he can handle landing out of an ILS at
night with a 10 kt tailwind, he can pretty much handle any straight in
visual segment.

I suspect if you cross the runway threshold right on the glideslope at 90
knots in a Skyhawk with a 5,000 foot runway, there is no way you could
overrun the runway if you tried.

I suspect you're right - as long as there is really 5000 ft of landing
distance available and no significant tailwind. However, lately I'm
seeing a lot of people flying the ILS at 100+ kts in Cherokees and
Skyhawks. I find this fascinating since it's faster than I fly the
ILS in my twin, unless I am specifically instructed to keep my speed
up.

Michael

French Bulldog? This is my idea of a French Bulldog:
http://www.jetphotos.net/viewphoto.php?id=191673

:-)

Paul

"Jeff" wrote in message
...
http://www.turboarrow3.com/newplane/chino/index.html

"Michael" wrote in message
om...

I suspect you're right - as long as there is really 5000 ft of landing
distance available and no significant tailwind. However, lately I'm

I would say an overrun cannot happen in a 172 on ILS into the wind or with
calm winds as long as the power is cut at decision height. If the airspeed
is high as discussed in this thread and the airplane is on the glideslope,
then the airplane should be within gliding distance of the runway at
decision height.

As far as flying an ILS with a tailwind, I agree that could cause an
overrun. I would also suggest that landing out of an ILS in actual IMC
conditions with a tailwind is an exercise which should be attempted only by
an experienced, advanced IFR pilot and/or with an experienced CFII on-board.
In particular, a pilot who is uncomfortable flying a high-airspeed ILS with
a headwind certainly should not attempt a tailwind ILS.


--
Richard Kaplan, CFII

www.flyimc.com

"Richard Kaplan" wrote
I would say an overrun cannot happen in a 172 on ILS into the wind or with
calm winds as long as the power is cut at decision height. If the airspeed
is high as discussed in this thread and the airplane is on the glideslope,
then the airplane should be within gliding distance of the runway at
decision height.

Yes, that's true. However, I consider an immediate power cut at
decision height to be poor procedure. The normal ILS is flown on a 3
degree glideslope. However, the power-off glide in anything
approaching landing configuration (meaning gear down if retractable
and at least some flaps) will be 7-10 degrees. So a power cut at DH
means a significant pitch change at low altitude. Since most of the
fleet has tractor props and conventional tails, the power cut will
also cause a significant out of trim condition - nose down. In good
vis and with a Skyhawk-class airplane, it's not a big problem. Try
that trick in your C-210 or my PA-30 in less than a mile vis, and
unless you've practiced it extensively and recently, the landing is
goint to be very, very ugly - possibly ugly enough for maintenance
bills. People have been known to drive the gear right through the
wings doing this.

Since my IFR students are either flying high performance singles or
twins or expect to move into them, I just can't see teaching the
procedure you seem to be advocating. I instead teach a gradual power
reduction with retrim, such that the pitch attitude never really
changes and the airspeed bleeds off gradually. Yes, it eats more
runway and on short runway may require a speed reduction on the ILS,
but it seems like a beter tradeoff. Personally, I slow to about
95-100 mph (not kts) on the ILS at about 300 ft, which seems like the
best compromise between retaining the option for a single engine
missed approach and allowing a landing with a tailwind on a short ILS
runway. In a single engine plane, I see no reason not to slow down
further out. I know that an ILS can be flown in a Bonanza at 90 mph
in turbulence - I've seen an instrument student do it.

As far as flying an ILS with a tailwind, I agree that could cause an
overrun. I would also suggest that landing out of an ILS in actual IMC
conditions with a tailwind is an exercise which should be attempted only by
an experienced, advanced IFR pilot and/or with an experienced CFII on-board.

Well, I like to give my student the necessary tools to handle it. Of
course since I don't instruct renters and don't deal with FBO's,
finishing in the minimum allowable 40 hours is not my highest priority
- nor theirs.

In particular, a pilot who is uncomfortable flying a high-airspeed ILS with
a headwind certainly should not attempt a tailwind ILS.

Now that I can agree with. A high speed ILS is certainly something I
consider important. It's just that a high speed ILS and a tailwind
landing on a short runway simply don't mix.

Michael

"Richard Kaplan" wrote in message ws.com...
ILS runways are usually 5,000 feet or longer. You could dissipate speed
over the runway.

I suspect if you cross the runway threshold right on the glideslope at 90
knots in a Skyhawk with a 5,000 foot runway, there is no way you could
overrun the runway if you tried.

I don't know about a Skyhawk, but FWIW, our former home airport
used to have only 1 ILS, to Rwy 8 which meant if low wx combined with
wind, one might be landing with a tailwind (prevailing winds from
west in these parts). As a training exercise, one time I kept my
speed up to 90 kts over the threshold. I didn't run off the runway,
but I was durn close to my "go around!" point before my plane
decided to quit flying and settle down. I definately landed on
the last 3rd of a 6,500 ft runway. Dunno what the tailwind was --
nothing too startling (10-12 kts?)

Unfortunately, since many training ILS are done to a missed
approach, landing from an ILS isn't something at which some
instrument pilots get a lot of practice.

Cheers,
Sydney

"Snowbird" wrote in message
om...

the last 3rd of a 6,500 ft runway. Dunno what the tailwind was --
nothing too startling (10-12 kts?)


That is a very significant tailwind for landing; it would not surprise me if
a 10 knot tailwind doubled your landing roll vs. a 10 knot headwind or if
the total landing distance increased between 50% and 100%.


--
Richard Kaplan, CFII

www.flyimc.com

"Richard Kaplan" wrote in message ws.com...
"Snowbird" wrote in message
om...
the last 3rd of a 6,500 ft runway. Dunno what the tailwind was --
nothing too startling (10-12 kts?)

That is a very significant tailwind for landing; it would not surprise me if
a 10 knot tailwind doubled your landing roll vs. a 10 knot headwind or if
the total landing distance increased between 50% and 100%.

Hi Richard,

As far as I could tell, it didn't do a thing to my landing roll.
What it affected, drastically, was the distance it took my plane
to slow to landing speed and consent to stop flying.

I'm very glad I had a CFI who had me try this. Experience is
worth 1000 words. After doing so, I can easily see how an overrun
accident (or loss of control if someone tried to force the plane to
land) could occur on a long, ILS-served runway.

One size definately does not fit all situations for ILS procedures.
I don't think it's a great idea to fly ILS routinely at 60 kts --
as someone pointed out, the margin over stall is much lower and
the configuration changes needed for correction much larger than
at 90 kts. OTOH, a practice of never retarding the throttle
until over the threshold (as I believe Rick Durden suggested)
would IMHO definately be a bad idea on a shorter runway (say
5000-6000 ft) w/ a tailwind.

And my advice to instrument students is: make sure you actually
land out of a good number of ILS in a number of different
circumstances,
preferably ILS in IMC or at night. For that matter, make sure you
land out of a variety of approaches.

Cheers,
Sydney

(Snowbird) wrote:
As far as I could tell, it didn't do a thing to my landing roll.

You may not have noticed the increase, but physics is physics. Most
spam cans touch down at about 50 kts, which means a 10 kt tailwind
increases your touchdown ground speed by 20%. Basic physics says that
will increase your ground roll by 44% for the same amount of braking
effort.

Everybody should try some downwind landings, if only to see just how bad
an idea they are. The problem is how. I don't like doing them at
uncontrolled fields, because you're going against traffic. The best way
is to find a towered airport at a time when there's nobody else around
and ask for the downwind runway.