Engine out, what is your vertical decent speed be in a forced landing?

Engine out, what is your vertical decent speed be in a forced landing?

  • 5 or less FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%
  • 6 FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%
  • 7 FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%
  • 8 FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%
  • 9 FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%
  • 10 FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%
  • 11 FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%
  • 12 FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%
  • 13 FPM Vertical speed at the end of 50 feet

    Votes: 0 0.0%

  • Total voters
    1

All_In

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PRA is collecting safety data and needs your help. This is a good excuse to go do some test flying.

The test flight:
  1. Ascend over a real landing site to at least 500 feet AGL. More if not a high time pilot.
  2. Practice= imagine your at 50 feet AGL cursing speed and your engine is out so pull power to idle but enter an true vertical decent for 50 feet and note your vertical decent speed.
If your rotorcraft is a model we do not have PRA will send you a data logger if you do not have an accurate means of knowing your vertical decent speed.

This is just the first test collection as a rough poll.

We will eventually post another thread and ask the pro's what real data points we would need to collect. EG Make, Modle, GW at the time of test, Density Altitude, Blades: Make, length & cord. etc.
 
When I lost my engine At less than 100 ft of altitude I tried to get a air speed of 60 mph which was impossible at that low of an altitude,

I went forward on the cyclic instantly when the engine lost power all I could achieve was about 45 mph as the ground came up to meet me

I came back with the cyclic to place the tailwheel on the ground as soon as that happened It was full back on the cyclic,I made one of the

best landings ever. As for my rate of descent I have no idea what it was,what matters is forward airspeed,without it at the bottom end of the landing

there is nothing to flair with. rate of descent is not the important thing airspeed is everything. My manuel says 60 mph with an engine out,nothing is

said about the rate of descent.
 
The really vertical descent is the worst rate of all: About 1700 ft / min
As Eddy said, the slowest descent rate is rather at 45 mph forward: about 900 ft / min , and the flare can almost cancel it.
Just my theoretical data, but it seems to me that this landing procedure should be the usual method. Thus the engine failure would never an event.
 
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No Title

I have not used a VSI that would give me that data John.

The VSI in The Predator has a lag as does the altimeter so figuring out what it is doing after 50 feet would be impractical.

If I wait for the VSI to stabilize I see around 1400 feet per minute in a relatively vertical descent (yaw string straight up).

With about 45kts indicated airs speed in a power off (engine at idle) descent I may see anywhere from 900 feet per minute to 1,400 feet per minute in The Predator.

When planning an emergency landing I use a three to one glide ratio. I have seen slightly over five to one. The wind can shorten the distance significantly. The glide ratio is better with the engine stopped. I have seen seven to one with the engine stopped and a little bit of a tail wind.
 

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During vertical descent, the rotor behaves like a parachute and it makes little difference on rate of descent whether the parachute is made from silk or nylon.

The attached chart by Prof. JAJ Bennett, chief engineer of Cierva Autogiros at the time, shows calculated rates of descent for a C-30 with rotors of various qualities.

Notice that for a rotor with zero profile drag, vertical descent rate is 29.1 fps while for a high drag rotor, rate of descent is 31.2 fps.
Rate of vertical descent is primarily a function of disc loading.

Chart from Principals of Helicopter Engineering by Shapiro.

vertical descent.JPG
 
Chuck, can you tell what was the load on this Shapiro's chart?
Thank you.
 
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JC, Prof. Bennett’s calculations were based on normal weight and standard rotor diameter for a C-30 but Shapiro does not provide details.

He provides this reference: Bennett, J.A.J. The Vertical descent of an Autogiro. Aircraft Engineering Feb, 1940, p. 40 .

I think Aircraft Engineering was a UK journal.

Specifications from Brooks: Cierva Autogiros for the C-30A (Avro 671) were:

Rotor diameter……………..37 ft.

Empty weight……………...1210-1464 lb.

Maximum takeoff weight….1800-1900 lb.
 
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Jean Claude;n1133405 said:
The really vertical descent is the worst rate of all: About 1700 ft / min
As Eddy said, the slowest descent rate is rather at 45 mph forward: about 900 ft / min , and the flare can almost cancel it.
Just my theoretical data, but it seems to me that this landing procedure should be the usual method. Thus the engine failure would never an event.

I did a test 1000-foot descent at zero forward airspeed last month (this is what is normally meant by "vertical" descent, no?), and it took about 35 seconds. That is just about 1700 ft/min, or over 28 ft/sec. This seems to comport with what is in Bennett's chart, but is nothing close to the choices given in the "poll" contained in the lead post here.
 
I do not know how to answer your poll, but here is a video of me having a Mac attack at 50'. Vertical decent at 50' can not be much because the ground is there before you have time to think about it.
https://www.youtube.com/watch?v=nd7xJV3nOsA
 
Thank you my friends it all helps. Should have just told you want we are up too and let you tell us what we need.

Think of the landing gear needed for drop landings like the butterfly and landing gears that may help with the modern gyro's tipping over.

We hope to encourage development of a light weight gear as one of our new Chuck Beady Engineering award contest.

For that I suspect we need to know the range if decent speed for drop landing... It appears we will need to send out the data-logger.

What else do we need to provide to make a designers job easy and this project successful.
 
C. Beaty;n1133431 said:
Specifications from Brooks: Cierva Autogiros for the C-30A (Avro 671) were:
Rotor diameter……………..37 ft.

Maximum takeoff weight….1800-1900 lb.

1700 ft / min in vertical descent for our gyros is consistent since proportional to the square root of the load per sq. ft
 
John no data, just an experience.

I have had one ‘for real’ engine out on the Bensen. It happened when after a sortie I came back to Rissington after about 45 mins. My 5 gall tank and 532 meant I had an endurance of approx 1 hr and so I figured I has another 15 mins.

Nice brisk wind of about 12-14Kts so at the threshold of 23 I began practicing low level engine failures. I had been slowly building up to the lowest alt I could have an engine failure and safely put the nose down to maintain 55 Kts then have sufficient rotor rpm to then flare and land gently.

At the time around 200’ was about the lowest. I had done about three when on the climb out to around my 200’' the engine...to my surprise, failed.

I do not know at what alt this occurred. Very fortunately with the previous practice events extremely fresh in my mind the nose immediately went down at the Bensen’s impossibly steep 45 degree glide angle, I plummeted down, flared and landed.

I will freely admit it was not the feather-like previous ones that I always attempt, nor was I as cool and collected as I had been, when it was a practice event. The sudden knowledge that this is now for real does subtly impinge upon the senses and the touch down was firm...but quite acceptable. As I sat there with the rotors winding down I though how could this be, I have at least 5 mins fuel left.

When I undid the harness and checked, there was indeed a smidgen of fuel remaining, what I had not taken into account was the fuel pick-up point and the attitude I was creating with my steep climb-outs in the wind.

I had exposed the pick up point and starved the engine momentarily creating the subsequent emergency

I re-started the engine and was able to taxi back to the hanger, slowly ruminating on what an idiot I was, and, how lucky I had been and, very grateful for previous practice.

Due to the paucity of instrumentation, ASI, ALT, and compass I have no knowledge of rate of descent. Judgement/expericence-wise I would say in the region of 1700'-2,000’’ fpm descent rate.

To my mind in this scenario ...at low alt, the ASI is your primary instrument. It gives you a primary indication of what you need in order to flare and have sufficient energy in your rotors to touch down in reasonably safe manner.

If you have inadvertently strayed into dead man’s curve, of alt/as/ and alt, then be prepared for hospital or mortuary. If you are at altitude, take your time go though your emergency procedures and good luck.
 
What I should have said in the previous post was, do not look for a rate of descent, look for an approach airspeed that will, in an engine out scenario, allow you to flare and have sufficient energy in your rotors to kill your rate of descent and land safely
 
All_In;n1133450 said:
Thank you, my friends, it all helps. Should have just told you what we are up too and let you tell us what we need.

Think of the landing gear needed for drop landings like the butterfly and landing gears that may help with the modern gyro's tipping over.

We hope to encourage the development of a lightweight gear as one of our new Chuck Beady Engineering award contest.

For that, I suspect we need to know the range if decent speed for drop landing... It appears we will need to send out the data-logger.

What else do we need to provide to make a designers job easy and this project successful?


What he is looking for is NOT the Terminal Velocity from a continuous vertical descent. (1700fpm.)
Consider coming to a complete stop in the air and then beginning a Vertical descent.
The question is, "What is your vertical velocity after descending 50 ft?" ( 1000fpm???)

Watch the landing at 3:30 in the video.
https://www.youtube.com/watch?v=GlyR-aSEuig

Now consider you have to execute an emergency landing and the only option is a Tennis Court surrounded by a 12 ft fence and ringed with 50ft. Trees and Power Lines.
The normal 60mph low angle approach to a 2 ft flare is not an option.
The only option is a normal approach to just over the trees to a full stop flare 50ft up followed by a vertical descent to a very hard landing.

Now let's design something that can handle that landing.
Rather than risking life and limb we are going to remove the rotor and just drop the airframe from a height that produces the impact we are looking for.

https://www.youtube.com/watch?v=_JMV-cF7hj8

I recall somewhere that certified aircraft have to be able to sustain a 600fpm rate of descent on landing.
600 fpm can be obtained by dropping the airframe from 20 inches.
It doesn't seem like a lot until you jump down from the second rung of a ladder and you realize that the third rung is now out of the question.

Now, we know that a 2 ft landing flare is not accompanied by the gyro dropping like a stone onto the runway at design limits.
It is just a mild bump. It takes about 5 feet to really get your attention because the rotor's residual lift slows the descent.

1700 fpm can be obtained by a 13ft drop. Now we are talking a second story window! Big Ouch!

So the award contest might specify that you need to demonstrate dropping an airframe from something more than 2 feet but less than 13.
That number is what we need to determine. Something like 52" (1000 fpm)???

How fast do you hit the ground if your flare to a full stop at 50ft and then descend vertically to the ground?. A 50ft Stop and Drop!

________________________________________
Just for fun... This one is painful to watch!
https://www.youtube.com/watch?v=tFqioA8OYCM
 
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This all helps very much my friends. U-ROCK!
 
How could you really measure this accurately? I don't know that my altimeter would be so accurate or maybe it would be me that wasn't so accurate, being able to know the altitude I achieved true zero speed. I feel like by the time I went from 55mph to 0 I would have probably lost 50 feet in the transition, no? I'll give it a go at a couple hundred and see maybe.

Perhaps a video?
 
N447MR;n1134996 said:
How could you really measure this accurately? I don't know that my altimeter would be so accurate or maybe it would be me that wasn't so accurate, being able to know the altitude I achieved true zero speed. I feel like by the time I went from 55mph to 0 I would have probably lost 50 feet in the transition, no? I'll give it a go at a couple hundred and see maybe.

Perhaps a video?

I would not try this at less than 1000 feet, you might be surprised at how quickly you can loose a couple of hundred feet.
You could go from 55 to zero and lose, hold, or even gain altitude depending on how hard you pulled back on the cyclic.

A video would be useful if you could view it frame by frame against a calibrated background.
The problem is that you will need to actually crash an airframe.

A data logger and a gps that outputs 10x per second would be safer.
Some Dynons log at 16x per second.
Flair to a stop at ~1000 ft and let it drop about 100 feet before recovering.
Check the logged data to determine the rate of descent after a 50ft altitude change.

This number is going to vary wildly for different gyros.
Light blades store less Kinetic Energy than Heavy blades.
A light gyro with heavy blades is going to descend like a feather.
 
Uncle Willie;n1135005 said:
This number is going to vary wildly for different gyros.
Light blades store less Kinetic Energy than Heavy blades.
A light gyro with heavy blades is going to descend like a feather.

The design of the landing gear will need to be capable of adjusting for different gyro weights and a wide range of descent rates.
 
N447MR;n1134996 said:
How could you really measure this accurately? I don't know that my altimeter would be so accurate or maybe it would be me that wasn't so accurate, being able to know the altitude I achieved true zero speed. I feel like by the time I went from 55mph to 0 I would have probably lost 50 feet in the transition, no? I'll give it a go at a couple hundred and see maybe.

Perhaps a video?

I've build a data logger from RC model components that PRA can mail to those helping collect data. It even takes the GPS data and converts it to a google map virtual tour we can share with the world of the testing or flying.

http://www.pra.org/images/Equipment/DataLogger.jpg
 
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