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  #71  
Old 07-21-2021, 02:07 PM
Vac Vac is offline
 
Join Date: Jul 2009
Location: Niceville, Florida
Posts: 491
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Hi Stan,

Yes we are. The AOA forum is on Friday 30 Jul 0830 Workshop Classroom A. We are also doing a HUD forum on Wed 28 Jul at 1300 in the Homebuilder's Hangar. We'll be at the beer tasting and Monday night social as well. Contact info is on the front page of our web site if you want to run us down.

Cheers,

Vac
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RV-4 2112
Niceville, Florida
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  #72  
Old 07-21-2021, 02:11 PM
wawrzynskivp wawrzynskivp is offline
 
Join Date: Feb 2018
Location: Incline Village Nv
Posts: 92
Default Theoretical turn back numbers based on actual findings

I think I've got this right, somebody chime in if you see a logical error.

In previous posts I laid out that my RV-7 and I have been tested and we need 650' at a DA of around 6000' to execute a 90-270 turn. In those same conditions on takeoff we covered 7,900' to go from stop to 650' AGL. I calculate that we make about 900' distance toward the runway in the turn.

Note that this discussion is assuming a straight out departure.

So theoretically on a 7000' runway I can make the threshold from 650' AGL in a DA 6000' or less.

But what if the runway is shorter? I'll finish the turn but well short of runway.

Comparing my 7:1 climb ratio beginning at 7,900' from the brakes release point at 650' AGL, with my 11:1 glide I come up with needing an extra 250' AGL for each 1000' increment of runway length less than 7000'

Example: Take off from a 3000' runway. At 650 I can execute a turnaround but will be 4000' short of the opposite runway threshold. I still need about 400' AGL once I finish the turn to glide the rest of the way. So the added numbers look like this: 4(k) * 250' +650' = 1650' AGL required to execute a turnaround and expect to make the threshold of a 3000' runway. Why so high? Because I'll be 2.7 SM from the threshold once I finish the turn around, and those are the numbers required to glide to make concrete.

If it's rural and there is plowed field then a turn around from less than that may be smart. But if it's warehouses at the departure end then it's 1650' AGL or forget about the runway.

To me that is a shocking bit of information! Surely 1,500' AGL is enough to turn back right? Not according to the math if the runway is typical for an RV.

My testing was done in the vein of normal operations. My takeoff wasn't max performance, it was a normal takeoff. My turns weren't practiced extensively, they were done with moderate proficiency. Surely the climb and turn numbers could be tightened up, but these represent what I will likely encounter in an unexpected loss of power on takeoff. Also there will be extra energy remaining the further you get from the runway and the more you can round off that 90-270 into more of a 15-195.

Good argument for VCOA

Food for thought.

Last edited by wawrzynskivp : 07-21-2021 at 04:54 PM.
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  #73  
Old 07-21-2021, 03:17 PM
larosta larosta is offline
 
Join Date: Dec 2010
Location: Redlands, CA
Posts: 188
Default AoA Instruments In Certified Training Fleet

Quote:
Originally Posted by PhatRV View Post
The Onspeed device works for our EAB, Vans, but for most of the training fleet comprised of older 172 and Cherokee, the OnSpeed device and precise AoA measurement aren't available. So the GA fleet relies on the power settings and reference speeds. I think this method has worked well for the GA, especially for teaching new pilots.
This is an interesting point. While not related to VAF interests directly it certainly could affect overall flight safety and acceptance in GA overall.

The FAA lowered the threshold and cost of installation in GA aircraft with their in 2014 that allowed installation of AoA systems and appeared to encourage it.

"Press Release FAA Clears Path for Installation of Angle of Attack Indicators in Small Aircraft"
https://www.faa.gov/news/press_relea...m?newsId=15714

"Approval of Non-Required Angle of Attack (AoA) Indicator Systems"
https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgPolicy.nsf/0/eb0fac0c1641509586257c76005e6274/$FILE/AIR100-14-110-PM01.pdf

I think that it in many cases comes down to: "I don't need it I am an excellent stick and rudder pilot and will never get into that situation", "The dammed C150 isn't worth that much, why should I spend even a few hundred dollars and it?", or "Our students have enough to be concerned about without an additional system to monitor,!", "We don't want/need to revise our training syllabus!", and the excuses go on and on.

Bottom line for me, there is no reason an AoA system could not be installed in every GA aircraft in the fleet if an owner our pilot wanted it. The FAA certainly lowered the barricades back in 2014.

- larosta
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  #74  
Old 07-21-2021, 05:39 PM
swjohnsey swjohnsey is offline
 
Join Date: Nov 2018
Location: Kingsville, TX
Posts: 391
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Quote:
Originally Posted by wawrzynskivp View Post
I think I've got this right, somebody chime in if you see a logical error.

In previous posts I laid out that my RV-7 and I have been tested and we need 650' at a DA of around 6000' to execute a 90-270 turn. In those same conditions on takeoff we covered 7,900' to go from stop to 650' AGL. I calculate that we make about 900' distance toward the runway in the turn.

Note that this discussion is assuming a straight out departure.

So theoretically on a 7000' runway I can make the threshold from 650' AGL in a DA 6000' or less.

But what if the runway is shorter? I'll finish the turn but well short of runway.

Comparing my 7:1 climb ratio beginning at 7,900' from the brakes release point at 650' AGL, with my 11:1 glide I come up with needing an extra 250' AGL for each 1000' increment of runway length less than 7000'

Example: Take off from a 3000' runway. At 650 I can execute a turnaround but will be 4000' short of the opposite runway threshold. I still need about 400' AGL once I finish the turn to glide the rest of the way. So the added numbers look like this: 4(k) * 250' +650' = 1650' AGL required to execute a turnaround and expect to make the threshold of a 3000' runway. Why so high? Because I'll be 2.7 SM from the threshold once I finish the turn around, and those are the numbers required to glide to make concrete.

If it's rural and there is plowed field then a turn around from less than that may be smart. But if it's warehouses at the departure end then it's 1650' AGL or forget about the runway.

To me that is a shocking bit of information! Surely 1,500' AGL is enough to turn back right? Not according to the math if the runway is typical for an RV.

My testing was done in the vein of normal operations. My takeoff wasn't max performance, it was a normal takeoff. My turns weren't practiced extensively, they were done with moderate proficiency. Surely the climb and turn numbers could be tightened up, but these represent what I will likely encounter in an unexpected loss of power on takeoff. Also there will be extra energy remaining the further you get from the runway and the more you can round off that 90-270 into more of a 15-195.

Good argument for VCOA

Food for thought.
I practice off a 6,000 runway near sealevel (128'). On the first take-off of the day I am off in 300 - 400' and make my crosswind turn before 500' AGL. On the next TO I have about 1,200' less so I am still on runway heading when I pull the power at 500' AGL, count 3, prop to low rpm, 90 mph and 45 degree bank into the wind. I maintain 90 mph. It usually puts me back to the runway about midway down. So once I see I have it made it is prop to high rpm and full flaps. I am usually high and fast so the concern is getting it down and stopped before the end of the runway. Also this will be a down wind landing.

Making it back to the runway is nice but most of what is inside the perimeter fence is better than what is outside. Lots of places to land on the airport that aren't runway in a RV, 'specially a tail dragger.
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  #75  
Old 07-21-2021, 06:04 PM
wawrzynskivp wawrzynskivp is offline
 
Join Date: Feb 2018
Location: Incline Village Nv
Posts: 92
Default Optimum glide with CS MT prop

In a previous post I posted some glide details for my set up.

I did glide testing with no fuel to the engine, prop full coarse, and believe it or not best glide involved better than 12" MAP.

Once I had the airspeed and rate of descent established I went back to idle glides and determined that idle and full coarse (1100 RPM) was adding considerable energy to my glide. In my set up I need to spin the prop at around 1400 RPM (by prop control) at idle power to get a rate of descent close to actual no power glide.

Hard to know how idling the engine compares to a true power loss until you try it. In my case there was a marked difference with the engine at idle and full coarse prop.

Everyone's airplane is going to show different power and glide performance, the key is to know yours cold.

Last edited by wawrzynskivp : 07-26-2021 at 01:54 PM.
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  #76  
Old 09-30-2021, 02:49 PM
YellerDaisy's Avatar
YellerDaisy YellerDaisy is offline
 
Join Date: May 2012
Location: Mountain Southwest
Posts: 194
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I've been working on this impossibility all summer with loads of practice time. There are obviously a bunch of variables and many of them have a very significant effect.

Here's a video of the impossibility in an RV-4 from 400' AGL (not maximum effort): https://youtu.be/zGY3uTsZ6mk
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  #77  
Old 09-30-2021, 05:16 PM
swjohnsey swjohnsey is offline
 
Join Date: Nov 2018
Location: Kingsville, TX
Posts: 391
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About the same as my RV-4 IO-360 CS prop. I have 6,000' to work with but I am usually way high so prop back to high rpm, full flaps and maybe a slip.
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  #78  
Old 11-25-2021, 03:37 PM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: Buena Park, California
Posts: 606
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I want to add to this thread about an actual successful impossible turn with an engine failure. While this is not a RV specific airplane, I am posting this because I learned a lot from watching this video because a lot of things went right with this emergency landing. There are a lot of video angles from this airplane, from the cockpit view to the outside view.

Airplane: Cessna Turbo Centurion. (Retractable gear. Gear retracted at take off and redeployed during the emergency landing)

Test Condition: 1st test flight after engine overhaul (remember what Mike Busch said about engine overhaul.)

Pilot: He is fully aware that he may have engine problem before the flight and was prepared to land when he encountered the engine failure

Landing: Landing was not on the same runway. The intersection runway was used and it meant he didn't turn as much if he had to land on the runway he took off from.

Picture of the flight track via ForeFlight.


The take off starts at 5 mins mark.

https://youtu.be/9FdRQiHyWQs?t=307
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  #79  
Old 11-25-2021, 08:18 PM
gmcjetpilot's Avatar
gmcjetpilot gmcjetpilot is offline
 
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Posts: 4,579
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Quote:
Originally Posted by PhatRV View Post
[snip] I am posting this because I learned a lot from watching this video because a lot of things went right with this emergency landing. There are a lot of video angles from this airplane, from the cockpit view to the outside view.

Airplane: Cessna Turbo Centurion. (Retractable gear. Gear retracted at take off and redeployed during the emergency landing)

Test Condition: 1st test flight after engine overhaul (remember what Mike Busch said about engine overhaul.) He blew a rod through the case. The data plate held the case together.

Pilot: He is fully aware that he may have engine problem before the flight and was prepared to land when he encountered the engine failure. I don't think he expected his newly overhauled engine to hand grenade, but agree he was on guard. He reacted quickly lowering nose and turning left (which was the best direction). He narrates I know you are not suppose to turn back.

Landing: Landing was not on the same runway. The intersection runway was used and it meant he didn't turn as much if he had to land on the runway he took off from. This saved the day. He departed Rwy 30 and landed Rwy 08. If he had to land on same runway Rwy 12, another 40 degree turn would have had him end up short of runway. He landed ON the threshold of the runway (with overrun).

Picture of the flight track via ForeFlight.

https://youtu.be/9FdRQiHyWQs?t=307
Good points. He also got slow in the turn and said in his narration he had to tell himself to push the nose down. That is where pilots FAIL and sadly stall and spin. Pilots close to the ground don't want to push the nose down and fly into a crash, and add task saturation a stall often occurs. I just completed my CFI renewal (15th renewal over 30 yrs) and there was much discussion in the renewal course work about turn backs, LOC (loss of control) and accident statistics.. The statistics show fatalities go way up if turn backs are made below 800 ft. Success rates although not 100% for turn backs at 800 ft or higher, did have lower fatalities.

If your climb rate is less than your glide sink rate you will never make the the runway. If you are light and really climbed at Vy you will be better off than at gross on a hot day.

The "180 degree" turn is really 270 degree if landing on same runway you departed in opposite direction.. Winds are high or obstacles around airport affecting that return decision should be thought of before takeoff and planned before takeoff.

If you lose the engine low and all runway is behind pick a place from 30 degrees left to right, and slow down, add flaps and fly the plane into the crash. If you get to 500 feet* pick a place 90 degrees either side for off field. Below 800 feet return to the same runway is iffy.

*Of course you see STOL planes making videos doing the simulated engine failure and return to runway at lower altitudes.

If you climb out at Vx you may have better luck getting back to runway. If winds are high you may overshoot the runway. If you are pitched to hold Vx and engine quits you better dump the nose NOW.
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Last edited by gmcjetpilot : 11-25-2021 at 08:28 PM.
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  #80  
Old 11-25-2021, 08:26 PM
swjohnsey swjohnsey is offline
 
Join Date: Nov 2018
Location: Kingsville, TX
Posts: 391
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Quote:
Originally Posted by PhatRV View Post
I want to add to this thread about an actual successful impossible turn with an engine failure. While this is not a RV specific airplane, I am posting this because I learned a lot from watching this video because a lot of things went right with this emergency landing. There are a lot of video angles from this airplane, from the cockpit view to the outside view.

Airplane: Cessna Turbo Centurion. (Retractable gear. Gear retracted at take off and redeployed during the emergency landing)

Test Condition: 1st test flight after engine overhaul (remember what Mike Busch said about engine overhaul.)

Pilot: He is fully aware that he may have engine problem before the flight and was prepared to land when he encountered the engine failure

Landing: Landing was not on the same runway. The intersection runway was used and it meant he didn't turn as much if he had to land on the runway he took off from.

Picture of the flight track via ForeFlight.


The take off starts at 5 mins mark.

https://youtu.be/9FdRQiHyWQs?t=307
I saw that. Guy didn't do himself any favors by dropping the gear before he was sure he had the runway made.
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