Use of FLaps in emergency situations

Hi, I've never been in these emergency situations, but have had a few
scenarios where it has come close enough to get me thinking what would I
do if the scenario was a touch worse (and, well, of course, how to avoid
getting that close in the first place). One thing I'd like opinions on
is the use of flaps. I don't see much talk of this in the POH. Now I
do mean to go up to altitude and practice some of this stuff, to see
what the airplane does, but would like to hear what the folks on this
group think about actions in these two dicey situations...

This is for C172R, with electric flaps going out to 30 deg..., if that
matters.


1 - Nice mostly stabilized approach, just a little steeper than the 3
deg VASI glideslope, 70K, 20 deg flaps, landing not assured yet, aiming
for the numbers since it is a shorter runway. Downdraft, windshear,
whatever makes me sink faster, so I push in the throttle... and the damn
engine sputters and quits.
Planned reaction: Intense focus on the airspeed, keep it as close to
60K, and _immediately_ retract flaps _but only_ to 10 degrees. Keep the
airspeed on 60K, expecting a need for back pressure due to the
now-retracted flaps. Then, 3-5 seconds later, divert attention first to
where ya gonna land, then second to why did the motor quit.
Rationale: the 10deg flaps will keep the slow flight without a stall,
and less drag than 20deg. Retracting from 20deg to 10deg will not
increase the stall speed much, and the only sink will be from the need
for more back pressure (anticipated). The goal here is to reduce drag
to increase options, ASAP.
If I was a little further out and wanted to stretch the glide more, I
think I'd accelerate to ~65K, and then pull all the flaps in as a last
step. With plans to dump them back out if the landing will be a crash,
i.e. won't make the runway.

2- Normal departure, 55K rotate, accelerate to Vy (~80K) when climbing
out of ground effect. For some reason, it's climbing like a dog, and
not sure going to clear obstructions.
First reaction: Slow down, just a bit, say 70 knots bringing one closer
to Vx to steepen the slope.
Second reaction (if that isn't going to be clearly sufficient): Dump 10
deg only of flaps, and slow right down to Vx, using the momentum to
climb up.
Rationale; I've always been taught that Vx climbs should be with 10deg
flaps to keep the stall further away. I don't see confirmation of this
in the POH (although the short-field obstructed takeoff is done with
10deg of course).

T

Tman wrote:

1 - Nice mostly stabilized approach, just a little steeper than the 3
deg VASI glideslope, 70K, 20 deg flaps, landing not assured yet, aiming
for the numbers since it is a shorter runway. Downdraft, windshear,
whatever makes me sink faster, so I push in the throttle... and the damn
engine sputters and quits.

I would retract flaps to 10 degrees while pitching as appropriate to
establish or hold best glide speed. *IF* you can hold best glide speed
and make the runway with the flaps fully retracted, it's better to do
that than keep in 10 degrees and hit the fence.

If I was a little further out and wanted to stretch the glide more, I
think I'd accelerate to ~65K, and then pull all the flaps in as a last
step. With plans to dump them back out if the landing will be a crash,
i.e. won't make the runway.

Pretty much.

2- Normal departure, 55K rotate, accelerate to Vy (~80K) when climbing
out of ground effect. For some reason, it's climbing like a dog, and
not sure going to clear obstructions.
First reaction: Slow down, just a bit, say 70 knots bringing one closer
to Vx to steepen the slope.

That's one way of expressing it, but an examiner or instructor would
think of it in terms of increasing pitch and (hopefully) rate of climb,
rather than slowing down.

Full power, mixture rich, carb heat off, MAGNETOS - BOTH... the latter
comes from personal experience... Then check your flap setting to make
sure they weren't dumped inadvertently.

By the time you roll out you've already checked the POH recommendation
for Vx, so you'll know immediately whether to set flaps for Vx. (You
probably will.)

You also already know whether it's a better idea to chop the power and
land on your remaining runway and risk hitting something relatively
slowly on the ground than at Vx 40 or 50 feet AGL.



-c

On Jul 15, 3:06*am, Tman x@x wrote:


2- Normal departure, 55K rotate, accelerate to Vy (~80K) when climbing
out of ground effect. *For some reason, it's climbing like a dog, and
not sure going to clear obstructions.

Why is it climbing like a dog? Did you not check density altitude? If
well past airfield you _could try to climb at 65lk (check RPM
flaps...) but why not just turn away from the obstructions? You are
at 80k so you can take 20 flaps and immediately start a canyon turn.

Cheers

On Jul 15, 6:08*am, gatt wrote:
Tman wrote:


By the time you roll out you've already checked the POH recommendation
for Vx, so you'll know immediately whether to set flaps for Vx. (You
probably will.)


In M & R 172 -no flaps for Vx climb. That may be the case for all
other 172's?

Cheers

On Jul 15, 3:06*am, Tman x@x wrote:


1 - Nice mostly stabilized approach, just a little steeper than the 3
deg VASI glideslope, 70K, 20 deg flaps, landing not assured yet, aiming
for the numbers since it is a shorter runway. *

This makes no sense to me. How can you be in a _stabilised_ approach
and not be assured of the runway? Why is the approach to the short
runway only slightly steeper than VASI -you must have some power on
with 20 flaps if that is the case aso why are you are not in the short
field config?. Best glide in a 172 is 10:1 = 6 degrees with no flaps
(you should know this) and if you are now on or below the VASI
glideslope you won't make the runway so pick a landing spot fast and
go for it.

Cheers

On Jul 15, 9:07 am, More_Flaps wrote:


My instructor pounded one lesson into all his students.
No matter what emergency the first requirement is to fly the
aeroplane.
Don't think about making the airfield or trying to extend the glide
The worst things in aviation are.
Runway behind you
Altitude above you
fuel in the bowser.
And fixation upon unusual events

This makes no sense to me. How can you be in a _stabilised_ approach
and not be assured of the runway? Why is the approach to the short

I didn't think a stabilized approach was a power-off approach. You can
be in a stablized approach, lose power, and the landing is not assured.
That's what I meant.

Do you do all your approaches at 6 degrees to avoid not making the
runway in the event of power loss? Doesn't sound like a bad policy, but
not what i was taught, and not always possible.

T

On Jul 15, 11:33*am, Tman x@x wrote:
This makes no sense to me. How can you be in a _stabilised_ approach
and not be assured of the runway? *Why is the approach to the short

I didn't think a stabilized approach was a power-off approach. *You can
be in a stablized approach, lose power, and the landing is not assured.
* That's what I meant.


Ah OK

Do you do all your approaches at 6 degrees to avoid not making the
runway in the event of power loss? *Doesn't sound like a bad policy, but
not what i was taught, and not always possible.


Yes, I think that generally all my approaches are steeper than 3
degrees and have minimal power on (I feel comfortable with ~1200 rpm -
don't forget carb heart in non-injected 172's), I start above the 3
degree glide slope and rely on flaps and decaying airspeed to bring me
onto the visual glide slope on short final. If you have a low energy
reserve style approach (i.e. less than 6 degrees slope in a 172) you
need to be sure power is available... Initial aim point is 1/3 down
the runway and I drop that toward the threshold as I approach short
final. I've seen a lot of flat approaches with power on at my local
field and they are often too fast too -remember in a 172R Vso is about
33k so 1.3 Vso is 44k. To fly at 50 k (or thereabouts) requires a
high nose attitude but watching 172s at my local field I more often I
see a very flat touch down (plenty of balloons too) where the mains
and nose wheel touch almost all together. As an exercise, how about
flying the plane at 44k at altitude with 20 or 30 flaps (and power to
hold altitude) to get a feel for the handling at low airspeed (the
first stall warning may peep intermittently). Then _holding_ that
airspeed chop power and see your rate of descent. The nose high
attitude adds lots of drag so you descend very fast and that's how you
can get it into a really short field over obstructions. Don't forget
to add the gust factor to these speeds (often ~5k in my experience)
for the real approaches. Also if you have a long runway work out the
POH stopping distances compared to runway markers and try to always
meet that performance. It should be possible to easily beat the POH
figures as most of the time you fly you are not at MTOW. Talk this
over with your instructor.

As I understand it, (and ATP's here may correct me) the 3 degree
flatter approach is better for jets who need to keep power on as they
have poor spool up performance.

Cheers

On Jul 14, 8:00 pm, More_Flaps wrote:

As I understand it, (and ATP's here may correct me) the 3 degree
flatter approach is better for jets who need to keep power on as they
have poor spool up performance.

And they glide better, too.

Dan

On Jul 14, 11:06 am, Tman x@x wrote:
Hi, I've never been in these emergency situations, but have had a few
scenarios where it has come close enough to get me thinking what would I
do if the scenario was a touch worse (and, well, of course, how to avoid
getting that close in the first place). One thing I'd like opinions on
is the use of flaps. I don't see much talk of this in the POH. Now I
do mean to go up to altitude and practice some of this stuff, to see
what the airplane does, but would like to hear what the folks on this
group think about actions in these two dicey situations...

This is for C172R, with electric flaps going out to 30 deg..., if that
matters.

1 - Nice mostly stabilized approach, just a little steeper than the 3
deg VASI glideslope, 70K, 20 deg flaps, landing not assured yet, aiming
for the numbers since it is a shorter runway. Downdraft, windshear,
whatever makes me sink faster, so I push in the throttle... and the damn
engine sputters and quits.
Planned reaction: Intense focus on the airspeed, keep it as close to
60K, and _immediately_ retract flaps _but only_ to 10 degrees. Keep the
airspeed on 60K, expecting a need for back pressure due to the
now-retracted flaps. Then, 3-5 seconds later, divert attention first to
where ya gonna land, then second to why did the motor quit.
Rationale: the 10deg flaps will keep the slow flight without a stall,
and less drag than 20deg. Retracting from 20deg to 10deg will not
increase the stall speed much, and the only sink will be from the need
for more back pressure (anticipated). The goal here is to reduce drag
to increase options, ASAP.
If I was a little further out and wanted to stretch the glide more, I
think I'd accelerate to ~65K, and then pull all the flaps in as a last
step. With plans to dump them back out if the landing will be a crash,
i.e. won't make the runway.

2- Normal departure, 55K rotate, accelerate to Vy (~80K) when climbing
out of ground effect. For some reason, it's climbing like a dog, and
not sure going to clear obstructions.
First reaction: Slow down, just a bit, say 70 knots bringing one closer
to Vx to steepen the slope.
Second reaction (if that isn't going to be clearly sufficient): Dump 10
deg only of flaps, and slow right down to Vx, using the momentum to
climb up.
Rationale; I've always been taught that Vx climbs should be with 10deg
flaps to keep the stall further away. I don't see confirmation of this
in the POH (although the short-field obstructed takeoff is done with
10deg of course).

T

"Somewhat" steeper than 3 degrees? As was pointed out, 172s don't
glide very well, and where I live we mostly are landing into a head
wind. 10 kts of wind will very significantly alter the glide angle
with respect to the earth. If your goal is to make the field should
you have an engine failure when you're somewhere past the numbers on
downwind you're going to have to manage energy a lot better than
you've indicated here., in terms of combining higher airspeed and
higher altitudes. A simple reality check is to simply pull back the
throttle close to idle passing the numbers downwind when you're number
one to land and getting used to the sight picture that'll get you to
the runway. I haven't flown a 172 in a long time, but seem to
remember any amount of flaps increased glide angle. I'd keep 'em up
until pretty late in the game.