Glide Speed - Flaps Up v. Down

[minitour]

Reviewing for a stage-oral in the 152, I was just checking myself on the "emergency" checklist items that (I feel) I should have completely memorized in case there isn't time to verify using the paper checklist.

One thing that hung me up was the "Emergency Landing (no Engine)" checklist.

My initial thoughts were:
Trim to 60
Troubleshoot checklist (re-start)
Then basically undo all the stuff you did in the re-start checklist for the emergency landing. Things like the mixture all the way out, shutoff valve, ignition off, throttle closed, etc...

What I missed was the airspeed and I can't figure out why it's different.

For every other checklist it's "Airspeed -- 60 KIAS" the first thing on the checklist. Well for this one it's "Airspeed -- 65 KIAS (flaps UP) 60 KIAS (flaps DOWN)"

I understand flying slower with flaps down to increase the glide ratio, but I don't understand why all of the other checklists use 60 and this one uses 65.

It's probably something really simple that I'm overlooking, isn't it?

-mini

 

[MarineGrunt]

Are we talking a checklist out of the POH or your school's checklist? Either way, go with the POH.

My only thoughts about the different airspeeds is that as your gross weight increases, so does your best glide speed.

 

[minitour]

Are we talking a checklist out of the POH or your school's checklist? Either way, go with the POH.

My only thoughts about the different airspeeds is that as your gross weight increases, so does your best glide speed.

The POH.

It's under "Forced landings" and "Emergency landing without engine power"

I just was going through the checklist kind of "dry flying" the plane and called out "60 knots" and then the rest. When I checked it, it was 65 with flaps up...totally blew my mind. It's the only checklist in here with a different glide speed ( I don't count the engine fire one b/c I'm setting a speed to put out the fire, not to glide).

Don't get it

-mini

 

[MarineGrunt]

Not sure. Maybe it means pitch for 60 until you get the plane cleaned up, then 65. Ask one of your CFIs who might be a little more familiar with the checklist.

Good luck on your check.

 

[Goose Egg]

I'd say do what the POH says, and definitely consult your CFI. It also wouldn't hurt to look up the old terms minimum sink speed and speed to fly (consult your nearest soaring manual.) But understand that there will always be a change in performance with a change in configuration.

-Goose

 

[midlifeflyer]

Different model year? Modifications? Looking at the best glide for failure after takeoff instead of emergency landing checklist?

The other piece is that best glide speed varies by weight. So the checklist "best glide" tends to be a ballpark number to begin with.

 

[minitour]

Thanks for the help! I'll see if I can find out what's up widit...if I find anything interesting, I'll let y'all know.

-mini

 

[Goose Egg]

The other piece is that best glide speed varies by weight. So the checklist "best glide" tends to be a ballpark number to begin with.

Too bad they don't publish a speed polar curve(s) for the 172. It'd be easy enough to make one yourself anyway.

-Goose

 

[uwochris]

The best glide speed is based the AOA where total drag is minized. With flaps down, you should reduce your IAS in order to maintain the max glide ratio. This is obviously contradictory to what the 152 POH says (Vg= 60knots, however, it mentions that the speed to use in the event of a forced landing for the approach and landing is 65 knots).

The only thing I can think of is the effect on the sink rate. Perhaps using 60 knots is more efficient, however, 65 knots gives a better result for the approach itself. With my experience in the 152, I know that if you were doing an engine out approach at 60 knots or less, you'd probably be coming down pretty fast. This is just a guess though.

 

[qmaster3]

One thing that hung me up was the "Emergency Landing (no Engine)" checklist.

My initial thoughts were:
Trim to 60
Troubleshoot checklist (re-start)
Then basically undo all the stuff you did in the re-start checklist for the emergency landing. Things like the mixture all the way out, shutoff valve, ignition off, throttle closed, etc...


-mini

MINI,

Another great memory aid that was taught to me.

A-B-C-D-E


Altitude

Best glide (I know this was your ??)

Choose landing spot

Diagnose-left to right on panel

Emergency-radio 121.5, mayday, kiss your ass goodbye, etc