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Emergency Descents

Emergency Decent Poll

  • Spin

    Votes: 3 3.2%

  • Slip with flaps

    Votes: 24 25.5%

  • Slip without flaps

    Votes: 8 8.5%

  • Dive with flaps

    Votes: 6 6.4%

  • Dive without flaps

    Votes: 34 36.2%

  • Other

    Votes: 21 22.3%
  • Total voters
    94
grantcarruthers

grantcarruthers

Well Known Member
What's the fastest and safest way to lose altitude?

Spin might be my first choice, better be good though

Full flap slip? Hard to mess up, likely not be faster than a spin

Dive

If you had to get down quick, what would you do
 
It would depend on why you want to get down so fast. If you had a structural problem and wanted to stay slow then flaps extended and idle would be best. If you want the very fastest way down a 6 G spiral dive at VNE would do the trick. Something more like 2 or 3 G's in a spiral down would however be much more comfortable and still allow for a high rate of decent.

George
 
IF you were smart and built your RV with a Constant Speed prop, all you need to do is push the RPM forward to high RPM and pull the throttle to idle. Now push the nose down. This is a TEST FLIGHT and EMERGENCY maneuver only! (done three times on my RV-6) I do NOT RECOMMEND it as a NORMAL or Standard Operating Procedure.

On my RV=6, I have a 45 degree down line, 4,000 FPM rate of decent, engine gauges are all in the GREEN and airspeed us UNDER REDLINE. Yes it is in the yellow zone at 180 KIAS. (Redline = 183 Kts)

Need to come down faster, then throw in some steep bank S-Turns.
 
RV6_flyer said:
all you need to do is push the RPM forward to high RPM and pull the throttle to idle. Now push the nose down. This is a TEST FLIGHT and EMERGENCY maneuver only! (done three times on my RV-6) I do NOT RECOMMEND it as a NORMAL or Standard Operating Procedure.

On my RV=6, I have a 45 degree down line, 4,000 FPM rate of decent, engine gauges are all in the GREEN and airspeed us UNDER REDLINE. Yes it is in the yellow zone at 180 KIAS. (Redline = 183 Kts)

Need to come down faster, then throw in some steep bank S-Turns.
Click to expand...

What is your FPM if you do all that, plus a 3G or 6G spiral? Sounds like that would be about max...ie. my feet are burning.
 
I seem to remember from the T-34 wing failure problems that pulling high g's while in a steep bank turn puts quite a bit of twisting force on the wings. Upset recovery courses usually teach to unload the wing before rolling level and then pull the g's, to avoid this stress. Any aeronautical engineers here that can comment?
I guess I would go to idle, push the prop forward, full flaps, and dive. I would use a slip in that configuration if I needed to go down faster. As others have noted, the reason one needs to get down fast will dictate the type of descent.
 
dmaib said:
I seem to remember from the T-34 wing failure problems that pulling high g's while in a steep bank turn puts quite a bit of twisting force on the wings. Upset recovery courses usually teach to unload the wing before rolling level and then pull the g's, to avoid this stress. Any aeronautical engineers here that can comment?
I guess I would go to idle, push the prop forward, full flaps, and dive. I would use a slip in that configuration if I needed to go down faster. As others have noted, the reason one needs to get down fast will dictate the type of descent.
Click to expand...

Yes, rolling AND pulling puts more stress on the wing with the down aileron than shows up on the G-meter. But in a spiral, you're not in the process of rolling (bank is already set), so this does not apply.
 
Cool, good info

Anybody have REAL numbers for rate of descent in a spin, in an RV

I've done a few turns in my -4 but nothing sustained to get descent speeds
 
RV6_flyer said:
IF you were smart and built your RV with a Constant Speed prop, all you need to do is push the RPM forward to high RPM and pull the throttle to idle. Now push the nose down. This is a TEST FLIGHT and EMERGENCY maneuver only! (done three times on my RV-6) I do NOT RECOMMEND it as a NORMAL or Standard Operating Procedure.

On my RV=6, I have a 45 degree down line, 4,000 FPM rate of decent, engine gauges are all in the GREEN and airspeed us UNDER REDLINE. Yes it is in the yellow zone at 180 KIAS. (Redline = 183 Kts)

Need to come down faster, then throw in some steep bank S-Turns.
Click to expand...


test flight emergency maneuver? I do it on almost every landing. abeam the numbers power to idle, prop full forward pitch for 80 mph and a nice constant turn to the numbers.

however, i agree doing it at 180kias is an e-ticket ride.

bob burns
RV4 N82RB
 
dmaib said:
I seem to remember from the T-34 wing failure problems that pulling high g's while in a steep bank turn puts quite a bit of twisting force on the wings. Upset recovery courses usually teach to unload the wing before rolling level and then pull the g's, to avoid this stress. Any aeronautical engineers here that can comment?
I guess I would go to idle, push the prop forward, full flaps, and dive. I would use a slip in that configuration if I needed to go down faster. As others have noted, the reason one needs to get down fast will dictate the type of descent.
Click to expand...


We used to refer to those as rolling pullouts. Its only a factor if you are rolling the aircraft at the same time your pulling high G's. In a spiral you are pulling G's with back stick but not rolling at the same time.
A good example of a rolling pull out would be if you were in a 30 degree banked turn and popped out of the clouds to see terrain ahead. In a panic you might snatch the stick back at the same time as you tried to roll level. This would put a asymmetric load on the wings. The proper thing to do would be to roll wings level and then apply G in the pitch axis.

George
 
One day a glider tow pilot showed me how they made a rapid descent. They'd put the old 180 hp Cub in a 90 degree bank, cruise power, using the elevator to maintain a relatively slow speed like climb speed, I think. The plane came down real well.

The airplane flew a turn since its wing was making lift in that 90 degree bank (the lift vector was oriented horizontally, of course), and there was no danger of thermal-shocking the engine since they carried power.

In an RV, I'd expect that pulling some gs would be good, since induced drag would be your friend.

Dave
 
Steep spiral

Before it shut down last year, I used to watch the tow plane from Sunriver Soaring descend at a crazy rate after the glider dropped away. I spoke to the pilot once and I think he said he used partial power, a 80* bank and about 3 gs to drop a few thousand feet in about 30 seconds. It sure looked like fun from the ground.

Something along those lines would be my choice, depending on the emergency, of course.
 
Spiraling Descent

This gives you the lowest amount of lift, helps you control your descent speed and airspeed. POH recommended, and I was taught this as part of my PPL. Good training anyway. Not as hard on the engine some believe as well, as it is not straight into the airstream, and (supposedly) less likely for shock cool. If I have to loose altitude fast, there is something wrong, and the engine, may have to suffer a little bit. I would gladly buy a new engine if it meant I walked away.
 
Smooth air or Rough?

Depends if you have smooth air or rough air. Don't forget maneuvering speed.
 
Our tow pilot descents...

Were as above at 80-90 degrees and 60 percent or so power and full top rudder (slip) and this kept the speed slow (75-80 knots) and the vsi in the 2000 fpm down range on our Citabria. :D
 
Reading about all these tow planes reminds me of one flight in my glider. Some &#*@ calls on the radio that he has released, and next thing I see is the tow plane in front of me starting to dive. Those are the moments when you are really quick on the release. :eek:

BTW, my Libelle has speed limiting air brakes. If I need to dive, I pull the brakes and push the stick forward. Vertical dive, 90 knots. I love that plane! :)
 
I've seen many skydiving videos where the jump plane rolls over and dives vertically with the skydivers for a few hundred feet before pulling away. No idea what effect they're having on the engine...
 
My data seems to contradicts RV-6Flyers ?

RV-8, XP-IO-360 and Hartzell BA VP Prop was just under 20degrees nose down to maintain Vne (200K). That equates to ~70K vertically down at MSL, ~6500fpm. At altitude, will be greater RoD due higher TAS at Vne.

I very much doubt either a spin, or flap dive (less than Vfe) would get anywhere near that RoD.

Some loading ('g') at Vne would increase RoD, but somewhat hazardous to fly.

Bear in mind that if it is "time to descend to X'" from cruise, the Vne dive has the added advantage of increased RoD whilst accelerating to Vne. The Vfe dive / spin require some delay to slow up to get in that condition.
 
Not great for your oil pressure (might not care in an emergency) if sustained, but anybody tried pulling power off, rolling to knife edge, and applying top rudder as required to control airspeed? Zero load on the airplane (1G on the vertical fin), and as long as you don't exceed Vne, you have some serious descent rate potential, since the wings are producing no lift.
 
Yep

I used to tow gliders in a Decathlon (traded for lessons) and that's exactly what we did but a little power was left on in order to not thermo-shock the heads and cylinders....like a brick it was!

Best,
 
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