At Spruce Creek right now....

[Jerry 5TJ]

1 hour ago, Fly Boomer said:

Airplane doesn't know how long the runway is but, depending on weight and environmental factors, it's going to take "X" feet to get stopped

True, so a fixed % rule is nonsensical. 

[carusoam]

FB,

You have an important point…

What the 50/70 rule does for us….

1) It gives us a way to ‘simplify’ the Go/stop now decision…

2) somewhat reliably starts the decision making as soon as practical… not waiting to be flying to make the decision.

3) somewhat increases our knowledge of the situation…. It magnifies the laws of physics for non-physicists… acceleration isn’t constant, and while we are accelerating… we sure are covering a ton of distance, while trees are growing larger in the windscreen…waiting on the last 10kias of acceleration… 

4) for best stopping distance… be going slow when starting the braking…

 

Soooo…

Using short runways… near 2k’ 

It is really important to know… to wait for the last 10kias, or be on the brakes…

 

Taken to the next level…

We have tools like WAAS and CloudAhoy… to know that are ships are conforming to POH numbers usually…

We discuss DA and OAT affects on power and lift… and have an ‘app’ /excel spreadsheet to calculate T/O runs…

So when the planes are not performing… brake brake brake…. 

Dragging the tail on the ground… is a subtle hint that things aren’t working correctly….

The final result indicates how the decision didn’t get made or executed…

Hoping to get off the ground… Hope is a terrible flight plan.

 

PP thoughts only, not a CFI…

Best regards,

-a-

[Pinecone]

You can stop faster than you can accelerate.  So if you make the decision at 1/2 the runway, you should be able to stop, no matter how short the runway is.  That is how this rule of thumb works.

And most runways have some reasonable overrun, so even if you go off the end at 10 knots, it is likely to be no big deal.  If you go off the end at 60+ knots, it is a MUCH bigger deal.

 

[carusoam]

What really helps…

1) Do the calculations a lot… before relying on them…

2) Be familiar with the resultant performance… so you know how reliable they are…

3) Do the calculations that day, and self discuss… the 50/70 rule and where the visual cue is on the airport…

4) It is going to be incredibly difficult to hit the brakes, when they’re only a few hundred feet of runway left…. Even when it is the safest result…

5) It also builds confidence in your skills, and your plane’s skills… to know when to say when…  because some days… the flight planning session is all it takes to cancel the flight… as DA increases as things get warmer…

6) With CloudAhoy/WAAS … every take-off is measured within feet…  we can actually judge how well our last performance matched expectations…

 

It will be really interesting to find out what was keeping this engine from performing to POH numbers…

 

Along with the trio of MP, RPM, and FF…. The 310hp engine also gives a small amount of tactile feedback… a seat of the pants feeling… 

PP thoughts only,

-a-

[carusoam]

7 minutes ago, Pinecone said:

You can stop faster than you can accelerate.  So if you make the decision at 1/2 the runway, you should be able to stop, no matter how short the runway is.  That is how this rule of thumb works.

And most runways have some reasonable overrun, so even if you go off the end at 10 knots, it is likely to be no big deal.  If you go off the end at 60+ knots, it is a MUCH bigger deal.

 

Stopping below 50kias is much better than above 50kias….  The non-linear aspect of things….

Above 50… our planes are so light on their feet… they easily lock the brakes and skid the tires…

Kind of a lesson we learn from our day to day operations… of Mooney landing….  

 

-a-

[carusoam]

Another rule of thumb…

If you have a Known engine performance challenge…

It is better to stay on the ground… because the performance isn’t going to get better in the air…

 

We had two similar Mooney accidents…

1) an M20K had a known issue of not producing full power… and failed to reject the T/O prior to hitting a berm at the end of the runway… (there is an ugly YT video for this one)

2) Patrick who taught us all about DA, and using all of the available runway in his M20J… (there were surviving passengers to recount the details)

Rejecting the T/O early would have been way better than not rejecting the T/O at all…

Best regards,

-a-

[carusoam]

For anyone not familiar with the 50/70 rule…

https://www.boldmethod.com/learn-to-fly/performance/how-to-use-the-50-70-rule-of-thumb-for-your-next-takeoff-this-summer/

a random video, that came up with a search…

Feel free to to provide a link, if you have a better resource…   

Best regards,

-a-

[Pinecone]

2 hours ago, carusoam said:

Stopping below 50kias is much better than above 50kias….  The non-linear aspect of things….

Above 50… our planes are so light on their feet… they easily lock the brakes and skid the tires…

Kind of a lesson we learn from our day to day operations… of Mooney landing….  

 

-a-

If you are over 50 knots, you are over the 70% range, so you would be taking off..

[carusoam]

I need to rethink a list of callouts…

1) Airspeed alive

2) MP, RPM, FF

3) 50/70… or is it at 70% look where you are… go/NoGo…

4) Vr

 

1 & 2 are probably reverse order to what I’m actually doing…

Short field operations occur incredibly rapidly… when things are going to plan.

Airspeed is primary for T/O, constantly scanning/monitoring on the way to Vr @65kias…

PP thinking out loud, not a CFI….

Best regards,

-a-

[Jim Peace]

Can it be easier just to use airspeed and RPM?  if you have nearly 2700 RPM can you assume you have good MP and FF?  

I still check oil pressure as well.....or is that overkill and better off to just use RPM & airspeed...

Also I have a JPI that shows % power...I always see near 100% for takeoff in my quick scan....can we just use that and speed?

 

[Pinecone]

Sometime you are on a long runway, see low low of MP you need to get full  RPM.

[hubcap]

My personal rule for my airplane -

MP - 36”

Airspeed alive

Fuel Flow > 22 GPH

55 KIAS by the 1000’ marks

Vr = 67 

[cbarry]

Just an observation, but it appears the empennage separate exactly at the rear bulkhead.   I’ve seen this on numerous wreckages of the same make and model.  I’m curious if the integrity of that joint has been fully sorted out?  Fortunately, the integrity of the fuselage did its job!

[jetdriven]

On 2/5/2023 at 2:26 PM, MooneyMitch said:

No doubt the pilot is beating himself up, knowing what a horrible decision he made that nearly caused tragedy for himself and his passengers.

Speed and flight can be very unforgiving.  It’s possible we forget these things as we travel in this fast world we live in.

Wishing a full complete recovery for these folks. 

 Not always. A very large percentage will claim the airplane wasn't running right through no fault of their own, then blame something else. 
and a lot of folks just aren't very mechanically aware.  Like that Bonnaza crash a couple weeks ago in NYC. He eventually caught on to the fact his plane was only climbing 200. Fpm but the flight data shows it was that way basically from takeoff. 

[EricJ]

42 minutes ago, cbarry said:

Just an observation, but it appears the empennage separate exactly at the rear bulkhead.   I’ve seen this on numerous wreckages of the same make and model.  I’m curious if the integrity of that joint has been fully sorted out?  Fortunately, the integrity of the fuselage did its job!

It's a pressurized airplane, so there's going to be a pressure bulkhead back there somewhere, probably just at the end of the cargo area, and that bulkhead may be stronger than those behind it.

 

[cbarry]

2 minutes ago, EricJ said:

It's a pressurized airplane, so there's going to be a pressure bulkhead back there somewhere, probably just at the end of the cargo area, and that bulkhead may be stronger than those behind it.

 

I realize the Malibu is pressurized (the Matrix version is not…), but other pressurized aircraft seem not to have an empennage separation issue such as this…

[tigers2007]

Is there a security camera that watches the runway there? It would be interesting to see the replay.

[Jim Peace]

1 hour ago, tigers2007 said:

Is there a security camera that watches the runway there? It would be interesting to see the replay.

yes....all angles from every direction has a camera on it....I have not seen the video yet but others have...

[carusoam]

9 hours ago, Jim Peace said:

Can it be easier just to use airspeed and RPM?  if you have nearly 2700 RPM can you assume you have good MP and FF?  

I still check oil pressure as well.....or is that overkill and better off to just use RPM & airspeed...

Also I have a JPI that shows % power...I always see near 100% for takeoff in my quick scan....can we just use that and speed?

 

The reasons for checking MP, RPM, and FF…
 

1) we can get full rpm without full MP, during the run… similar to departing a higher altitude airport…

without full MP… we are not making the HP we are expecting…

 

2) we can get full MP without full RPM…. Similar to an O1 that uses 2500rpm…

without full rpm… we are making 10% less hp… but our T/O run is 50% longer than expected…

 

3) we can get full power without full FF… similar to having a blockage, or not resetting the mixture properly…

without full FF… we are risking being in the red box, followed by high CHTs and detonation… or so lean we have gone LOP and not getting full HP either…

 

The important thing to recognize… it only takes a 10% reduction of total hp, to increase the T/O run 50%

Take off and climb… are all about excess hp…  and losing a small amount of the designed in excess hp isn’t really easy to notice

 

these numbers were taken from the POH supplement of the 310hp 2700rpm Standing Ovation upgrade…  where 280hp and 2500 rpm are standard for the O1…

then demonstrated using a WAAS SkyRadar combined with CloudAhoy… performance app and sensor…

also confirmed the findings using @Cris’ Screamin’ Eagle….  (A test of the app and sensor again, prior to blowing the big AMUs on the 310hp upgrade)

Somewhat lightly loaded similarly…  two people, half tanks…

The O1 T/O distance is 1200’

The O3 powered O1 and Eagle T/O distance is 800’

 

Two similar power problems I have experienced…

1) The M20C with a stuck, bent, valve not wanting to climb… with two on board… occurred just after several hundred feet in the air…. A major loss of most of the excess power available. Plenty of vibration indicating there was a problem…

2) A C152 missing a mag, max altitude was about 2k’ agl…. A surprising shortage of excess hp…. No engine monitor to give a hint of what was happening…. Leaning more would probably been helpful…

 

It doesn’t take much loss of power to ruin your day…

And if your plane is heavy, your power is low, by design… you may be planning to use 75% of the runway when everything is going well…

There won’t be enough room for even a 10% reduction in power…

Review as many hints as you can multi-task…. But, Don’t be heads down and off the centerline, these trees are even closer.

Note, it is pretty easy to get a tail strike with a long body during the T/O run…  some planes will do strange things when you pull back hard with airspeed…. Not enough speed to fly, but plenty of speed to drag the tail….

PP thoughts only, not a mechanic or a CFI… and not a reference to the accident or plane in this thread…

Best regards,

-a-

[Mooney in Oz]

17 hours ago, Jerry 5TJ said:

The compass rose at CA35 happens to be a highly visible point early in the takeoff roll.  For me it served as a checkpoint for proper acceleration and from which it was still possible to stop on the remaining runway.  

Without an accelerate-stop performance chart in the AFM you must make your own estimates.  

Thanks Jerry. That makes sense. At my home airport, I use the location of a taxiway where it intersects with the runway about half way along as the speed reference point.

Just as a matter of interest, is that compass rose located about the half way point of the runway at CA35?

[Mooney in Oz]

16 hours ago, Fly Boomer said:

I have read about the 50/70 rule here on MooneySpace, but I don't really understand the logic.  It seems to me that it's going to take the same amount of (remaining) runway to stop my airplane regardless of the runway.  Airplane doesn't know how long the runway is but, depending on weight and environmental factors, it's going to take "X" feet to get stopped.  I'm generally a fan of "rules of thumb" but it seems like it would make more sense to say "If I'm not off the ground when I have "X" feet of runway remaining, abort".  Anthony, I'm not picking on you specifically, this is really a question for the group.

G’day Fly Boomer.

My home airport runway is sealed and 1,000 metres (3,300 feet) long, so half way works for me.  But, you are right and common sense needs to be applied, particularly when estimates are used.

[Jerry 5TJ]

3 hours ago, Mooney in Oz said:

Just as a matter of interest, is that compass rose located about the half way point of the runway at CA35?

IIRC It’s perhaps 500’ from the start of the takeoff roll on runway 4.  

[Fly Boomer]

7 minutes ago, Jerry 5TJ said:

IIRC It’s perhaps 500’ from the start of the takeoff roll on runway 4.  

At an unfamiliar airport, or in the absence of a “marker” to judge where you are on the takeoff roll, is it enough to verify MP, RPM, and FF?  Information that’s available long before the 50% point, or whatever marker you are using.  I’m trying to imagine what would keep me from accelerating if I’m producing 100% power.  I guess the percentage of runway behind you would be useful if you were taking off downwind or uphill.

[Jerry 5TJ]

2 hours ago, Fly Boomer said:

….  I guess the percentage of runway behind you would be useful if you were taking off downwind or uphill.

Runway behind you is of no interest.  

[Pinecone]

8 hours ago, Fly Boomer said:

At an unfamiliar airport, or in the absence of a “marker” to judge where you are on the takeoff roll, is it enough to verify MP, RPM, and FF?  Information that’s available long before the 50% point, or whatever marker you are using.  I’m trying to imagine what would keep me from accelerating if I’m producing 100% power.  I guess the percentage of runway behind you would be useful if you were taking off downwind or uphill.

Anything you have is good.

The 50/70 is just another tool in the toolbox.  

If you fly off of IFR marked runways, you have a 1000 foot marker.   In the USAF we had a 1000 foot check speed.  If you were not at or above a certain speed at 1000 feet of takeoff roll, you aborted the take off.