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Author Topic: Video: Fatal Take-Off  (Read 43491 times)
Fryy
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« on: September 18, 2007, 03:32:30 AM »

Saw this in another forum and found it interesting considering all factors involved.

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moto400ex
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« Reply #1 on: September 18, 2007, 09:31:08 AM »

Thats odd that they would blame warmer weather for the plane not being able to climb although it is possible.  It looks like the plane stalled shortly after lift off.  How many people were onboard? The plane may also have been overloaded.
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Biff
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« Reply #2 on: September 18, 2007, 10:55:01 AM »

It's called Density Altitude and it's been a factor in plenty of crashes just like this one.  It usually does result in a stall because the aircraft can't generate enough lift to climb out, and you can't exactly fly cross country in ground effect.
« Last Edit: September 18, 2007, 10:57:48 AM by Biff » Logged

moto400ex
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« Reply #3 on: September 18, 2007, 12:04:07 PM »

ohh density altitude... i always fly around in ground effect so i dont need to worry about that.
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moto400ex
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« Reply #4 on: September 18, 2007, 12:10:07 PM »

That ladies description of what happened how it crumbled in the sky was a prime example of how observers that report witnessing an accident to the FAA tend to over exagerrate what happened.
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KSYR-pjr
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« Reply #5 on: September 18, 2007, 01:17:29 PM »

ohh density altitude... i always fly around in ground effect so i dont need to worry about that.

LOL, although technically speaking even if you did have a craft that only flew in ground effect you would still need to be aware of the effects of DA on your craft's capability to generate lift.   Place a Cessna 150 at a runway with a density altitude of 15,000 feet and you most likely are not even leaving the ground to enjoy ground effect.
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Regards, Peter
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pocho
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« Reply #6 on: September 18, 2007, 07:35:07 PM »

I have had instances where I've had to cancel cross country flghts due to the extreme heat (115F-120F) and high humidity levels, in a 172.

Hotter air -> high humidity -> less dense air = less lift. And of course, a heavily loaded plane creates a dangerous situation.

Now it's a bit cooler here, thankfully. We just saw double-digit highs for the first time in months, today.
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moto400ex
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« Reply #7 on: September 18, 2007, 08:36:27 PM »

Of course I understand the concept of density altitude.   Im a commericial multi instrument pilot I dont need an explanation.  Its just not too often Ive heard of that being the cause of a crash.
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KSYR-pjr
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« Reply #8 on: September 18, 2007, 09:06:51 PM »

Of course I understand the concept of density altitude.   Im a commericial multi instrument pilot I dont need an explanation.

Well, until Dave figures out a way to put all of our extensive aviation resumes next to our forum moniker you are just going to have to be patient with those of us who don't know your lengthy credentials after reading all 14 of your posts.

Its just not too often Ive heard of that being the cause of a crash.

BS.  Every commercial, multi instrument pilot would definitely know that the effects of DA can lead to a crash.  In fact, every private, non-instrument, non-multi would know that.  I ask this in the least derogatory way possible:  Are you rated in real life or MSFS?
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Hollis
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« Reply #9 on: September 18, 2007, 09:54:59 PM »

Not to muddy the waters any further, but assuming no mechanical or engine problem, that accident was caused by an overweight aircraft trying to fly in atmospheric conditions not adequate to provide a positive rate of climb out of ground effect. Three factors: reduced wing lift, reduced propeller thrust and substantially reduced engine output HP.
For a demo, climb to a safe altitude, with full power on, trim out at about 5 knots above stall for your weight, then pull on full carb heat and watch what happens.
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moto400ex
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« Reply #10 on: September 18, 2007, 11:39:52 PM »

Well If you read what I wrote first I never said that it was not possible.   I didnt go into detail about density altitude as i am not familiar with the area where the plane departed from and the conditions that it tryed to depart in. (It says warmer air) But it also says the plane was headed for mexico hinting that it also could be overloaded with god knows what.  Most of my flying is done on the east coast and midwest so density altitude has never been a big concern as field elevations are relatively close to sea level.  And yes I do realize that I am low on the totem pole here at liveatc.net as I have just gotten into looking at forums about atc.  Yes its easy to question my certificate and ratings but I have no reason to lie about it.  Unfortunalty I couldnt pass my private pilot checkride in flight simulator so I am obviously not rated there but it does help for anyone doing instrument training.  I have recieved all my training from an accredited university.  I just recieved my commercial cert last semester.  Our university plans it out so you get your commercial instrument multi all in one checkride.
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KSYR-pjr
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« Reply #11 on: September 19, 2007, 12:31:30 PM »

Well If you read what I wrote first I never said that it was not possible.   

I read what you wrote and what you stated was this:  "Its just not too often Ive heard of that being the cause of a crash."  If you truly understood the concept of DA, you should have absolutely no problem with that being listed as a factor in this or any crash. 

In an earlier post I see that you asked about the meaning of "Nordo," which should be another easily recognizable concept to those who are rated to fly.  If you really are commercial, multi-engine, instrument-rated pilot might I humbly suggest that you do your potential passengers a favor and get some actual left seat time to accumulate more than just book experience?  They and all of GA (which has a less-than-stellar reputation among the masses thanks to many high-profile accidents) will be most appreciative.
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Regards, Peter
ATC Feed:  Syracuse (KSYR), NY
Hollis
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« Reply #12 on: September 19, 2007, 12:56:33 PM »

The NTSB report:

My comments -
Density altitude computes to at least 3800 ft.
Maximum TOGW at SL = 3650 lbs. His TOGW computes to 3638 lbs.
Max SL HP is 300. His max available TO HP computes to 285.
Due to the lower HP and air Density ratio combination, his max propeller thrust available was less than 90% of SL rated thrust.
In effect, his maximum rate of climb out of ground effect was NEGATIVE!


* N1098F crash.jpg (172.01 KB, 800x624 - viewed 189 times.)
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moto400ex
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« Reply #13 on: September 19, 2007, 01:46:09 PM »

Well  I have 230 hours total time about and I fully understand the concept of density altitude and the effect it has on aircraft of any kind.  Im sorry I havent read too any ntsb reports about aircraft crashing due to density altitude.  I will try to research to try and further my knowledge about this.  I still never said anywhere that it wasnt possible not sure where you are finding that...  About Nordo I have never heard it in my flying and it not in any training course outlines that I know of for me.  I asked my Multi intstructor and had never heard of it so I proceeded to ask some people in the air traffic control department where I got an answer from a controller who has worked in denver center.  Ill ask my CFI teacher today shes and ATP and see if she knows... Ill let you know smiley
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KSYR-pjr
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« Reply #14 on: September 19, 2007, 02:12:33 PM »

My comments -
Density altitude computes to at least 3800 ft.
Maximum TOGW at SL = 3650 lbs. His TOGW computes to 3638 lbs.
Max SL HP is 300. His max available TO HP computes to 285.
Due to the lower HP and air Density ratio combination, his max propeller thrust available was less than 90% of SL rated thrust.
In effect, his maximum rate of climb out of ground effect was NEGATIVE!

Hmmm, not exactly sure how you arrived at a negative climb out rate.   Not necessarily doubting you as this reads to me like some kind of theory from aeronautical engineering but could you expand a bit and show your work.  Smiley

In a more practical sense, GA aircraft are delivered with takeoff and landing distance charts in the POH that a pilot is supposed to use to calculate take off distance needed.    The charts are normally designed so that no complicated math is needed.  Taking into account wind direction and speed, density altitude, take off weight,  slope of runway, and any obstacles at the end of the runway, a pilot can derive safe takeoff distance using these charts.

It is suggested that pilots add anywhere from 20 to 50% to the takeoff distance pulled from these charts to account for the fact that these charts are produced under the best possible conditions (new engine, test pilot skills, properly inflated tires, etc.).  Therefore, if the takeoff conditions resulted in a chart-derived TO distance of (for example purposes only) 2,700 feet, one would add a fudge factor of 540 feet up to 1,350 feet, or a total distance of 3,240 to 4,050 feet of runway distance needed.

A tip I read from a well-known mountain flying guru is that if you reach about 70% of takeoff speed within 50% of the runway, continue the takeoff.  Otherwise, abort.  Of course, this requires a pilot plan the takeoff enough to know where the halfway point of the runway is and have the confidence enough to abort with a plane full of passengers wanting to get to their golf outing.






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Regards, Peter
ATC Feed:  Syracuse (KSYR), NY
moto400ex
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« Reply #15 on: September 19, 2007, 07:10:00 PM »

Well to KSYR-pjr Ive asked my CFI teacher she says has heard the term before when she was flying as she was a Northwest airlines F/O.  Its not a term they teach in any of my aviation courses that I know of here although it seems to be widley accepted term in ATC. 
« Last Edit: September 19, 2007, 07:14:39 PM by moto400ex » Logged
mk
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« Reply #16 on: September 19, 2007, 07:24:24 PM »

There was a Bonanza crash last week most likely due to overgrossed conditions and density altitude. 

Elizabethton, TN.  http://www.ntsb.gov/ntsb/brief.asp?ev_id=20070907X01326&key=1

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Hollis
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« Reply #17 on: September 19, 2007, 07:48:21 PM »

An identical Model aircraft under nearly the same flight conditions, and the exact same results.
I'd say that pretty much tells the story!
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KSYR-pjr
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« Reply #18 on: September 19, 2007, 09:02:38 PM »

There was a Bonanza crash last week most likely due to overgrossed conditions and density altitude. 

I came across that one the other day while perusing the accident database.  Man, that sucks.  Five people dead.  This is the type of accident that just destroys GA in the eyes of the non-flying masses.
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Regards, Peter
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KSYR-pjr
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« Reply #19 on: September 19, 2007, 09:04:39 PM »

Well to KSYR-pjr Ive asked my CFI teacher she says has heard the term before when she was flying as she was a Northwest airlines F/O.  Its not a term they teach in any of my aviation courses that I know of here although it seems to be widley accepted term in ATC. 

Very good.  Like I alluded to before, nothing beats book smarts like actual experience.  Get out there and fly somewhere.
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Regards, Peter
ATC Feed:  Syracuse (KSYR), NY
moto400ex
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« Reply #20 on: September 19, 2007, 09:39:42 PM »

Ill agree with you there... its hard to get out and fly somewhere else while I am at school as most of my flying takes place locally and there are very few cross country flights I can actually do right now.   Ive only been flying for 2 years so yes im relatively new.  I guess the most experience I will get is out in the real world when I get a job.  I guess you could say its a downside to going to an aeronautical university.  You are very limited on where you can go and what you can do. 
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RayZor
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« Reply #21 on: September 19, 2007, 09:50:38 PM »

let me share with you a little story...

a few weeks ago i took my cfi, my friend, and a full load of fuel up in a 1973 warrior.  the temperature was 105 degrees.  we had 6500 feet of runway to work with, so my cfi thought it would be a good lesson....it took almost the full length of the runway to build up enough speed to establish a safe climb...6500 feet!! 

Don't be fooled...Density Altitude kills pilots.
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Hollis
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« Reply #22 on: September 19, 2007, 10:05:09 PM »

A good lesson for sure! You were lucky though - you're CFI was pushing the envelope just a wee bit there.
For anyone wanting to experience the effects of density altitude, try this when you have some spare time:
Do a normal full throttle take-off and note the time and distance to your lift-off speed. Now try the same thing but using only constant 80% power from brake release (but be prepared to firewall the throtttle just in case).
Been there, done that...

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CFVDI
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« Reply #23 on: September 20, 2007, 02:05:16 PM »

I did know the meaning of NORDO but decided to see how quick I could locate the info. by using google.  In a few seconds the explanation was on my screen.  Give it a try.
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moto400ex
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« Reply #24 on: September 20, 2007, 04:28:09 PM »

Oh really... whats google never heard of it before.... is it another atc site?     tongue
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