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Are Flex / De Rated take offs safe?

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Are Flex / De Rated take offs safe?

Old 20th May 2008, 08:28
  #61 (permalink)  
 
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You guys want to run the planes to the end of the runway to squeeze some more time out of your engines..fine...but the rest of us don't...and look at our safety record....not to bad huh?
Give us some numbers. I really want to see your safety record. And no, not that of your singular outfit but that of GA in general compared to airlines in general. Are you really sure you can beat airlines?

Taken from the NTSB database,

Accident rate for 100.000 flight hours (there is no data as to departures and miles for part 135 non scheduled service)

CFR 135 non scheduled (on demand air taxi as they call it)

2005 1.70
2006 1.42
2007 1.69

CFR 121 scheduled (airline service)

2005 0.176
2006 0.139
2007 0.128

You might want to enlighten yourself on http://www.ntsb.gov/aviation/Stats.htm.

Doesn't really look like your safety record is so outstanding compared to airlines after all, perhaps you should print out those figures and give them to your owner to read up while you do your TOGA takeoffs.
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Old 20th May 2008, 08:44
  #62 (permalink)  
 
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You said Flex when you spoke of a 50% reduction. Flex being Airbus's equivalent of Boeings assumed temperature reduced thrust. The max reduction is 25% as far as I am aware.

A de rate is different to flex and some operators use it to get around VMCG problems. You can add flex to your derate in which case, granted, you may well get down to something like 60% of full rated thrust. However not all operators have derates available to them or if they do use them. I believe they're used to balance up engines (we could have a mix of 20K and 22k engines a while ago so you de rated the 22k down to 20K to match the other one), address a VMCG problem or restrict a very light powerfull aircraft to normalish performance in a busy ATC environment. I think thats correct but others will have much more experience of de rates than me
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Old 20th May 2008, 08:49
  #63 (permalink)  
ssg
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Corporate is the safest sector...look it up...

In the mean time...some bedtime reading for you ...

In early March, CNN obtained documents from the House committee investigation that alleged the discount airline kept dozens of aircraft in the air without mandatory inspections -- and in some cases, with defects the inspections were designed to detect.

Boutris and Peters said FAA managers knew the XXXXX planes were flying illegally and did nothing about it, according to the documents.

The airline also flew at least 47 planes beyond a mandatory inspection of the fuselage, or skin, of the planes for possible cracks, the inspectors said. When the inspections were carried out, six of the planes were found to have possibly dangerous cracks, they said.

------------------
Gosh just makes you wanna go out and fly on an airline doesn't it..I mean the total committment to safety, the stand up professionalism....wow...very impressive...
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Old 20th May 2008, 09:06
  #64 (permalink)  
 
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Corporate is the safest sector...look it up...
Nah, if you're so sure of that why don't you just give us the numbers? You surely have them at your fingertips.

Yes, the FAA really let things slip by and all that stuff happened. And surprisingly enough the statistics from the NTSB (which is independent from the FAA by the way) still shows CFR 135 operators producing more than 10 times the number of accidents than airlines do per 100k flight hours.

I really would love to see your figures proving me wrong, best if they come from a respected source like the NTSB of course.
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Old 20th May 2008, 12:01
  #65 (permalink)  
 
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Besides if flex ever did get popular in corporate, which it's not
Incorrect....... we also operate a corporate fleet with both fixed and assumed temperature thrust reductions. You have this fixation that our aircraft will scrape over the fence, believe me, they dont!

Mutt
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Old 20th May 2008, 13:27
  #66 (permalink)  
 
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Minimum Flex

Using TOGA for takeoff cannot possibly be the safest way.

Logically using the ultimate derate - down to 0% power is the most safe, as you can securely sit around on your stand without going through all this risky flying business.

Of course, your passengers might murder you..

OORW
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Old 20th May 2008, 14:40
  #67 (permalink)  
ssg
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Mutt, You have never seen airliners routinely use up all the runway to get off?

The US corporate fleet isn't allowed to run thier engines out to 20000 thousand hours based on the say so of a guy with a boroscope...engines come off at time and cycle limits...there is no incentive to reduce power for take off to extend engine life, because, the engines come off when they come off, evidentely, thousands of hours before the airliners do.

While reduced power is available in some of the larger corporate jet, it tends to be used, as I have,...when the runway is very long, the airplane is light, the assigned alt is very low, nice day...ect ect...and the numbers are such that balanced field for the reduced numbers usualy have another 5000 ft added to them...very safe..

While I can't speak for all corporate operators, any more then anyone here to can speak for all airline operators, I have never in 20 years of flying had anyone tell me they were reducing thrust so they could 'add reliability' to thier engines...I have never seen anyone burn up more runway using reduced thrust so 'thier flight will be safer'

Last edited by ssg; 20th May 2008 at 14:52.
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Old 20th May 2008, 15:13
  #68 (permalink)  
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SSG

Sir- I'm honestly interested in your opinion, my friend flies the X for a local Company, loves the power and mystique.

Your last post was directed to Mutt, but if I may, could I ask you a couple questions?

I have seen airliners of all description "use all the Runway". I have seen a video of a Tupe using the overrun, launching a climb at 200fpm, scary.
If the discussion is about V1, my assumption is that when the crew calculate the numbers, the Runway Length is a definite player. I am not clear what consideration you are giving to the takeoff roll Post V1, doesn't that involve using addl Runway? Once V1 is attained, and I think this is important, what you are looking for is enough Runway left to Launch, not enough left to stop. All considerations relative to Takeoff have a "fresh" point, a time certain where they become irrelevant, as the Flight has transitioned from a Truck with Wings to an Aircraft with wheels. I may not be understanding all your posts, but I am left with the conclusion that you are demanding that the Runway left after V1 be of sufficient length to allow a stop. It is Not. It isn't supposed to be. Am I missing your point?

I should have posted this on the V1 thread, my apologies- Airfoil

Last edited by airfoilmod; 20th May 2008 at 15:29.
 
Old 20th May 2008, 16:51
  #69 (permalink)  
 
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but I am left with the conclusion that you are demanding that the Runway left after V1 be of sufficient length to allow a stop.
Last time i counted, there were 5 versions of the FAR detailing accelerate stop requirements, YOUR aircraft may have been certified to a different standard to the one parked beside you, so in some cases, you are allowed to pass V1 and react, but in more modern aircraft, it is assumed that VEF occurs 1 second prior to V1 and that you have initiated your action by V1. The Boeing Takeoff Safety guide advocates that if you reach V1, its go time!

You have never seen airliners routinely use up all the runway to get off?
Right from the cockpit, its amazing how rapidly a Classic747 eats up a Field Length Limited runway

I have never in 20 years of flying had anyone tell me they were reducing thrust so they could 'add reliability' to thier engines...I have never seen anyone burn up more runway using reduced thrust so 'thier flight will be safer'
You obviously havent spoken to the right people Here ended the discussion as we will never convince you until such time that you start flying an aircraft where the engine life isnt constant

Now considering that you consider us dangerous, i will give you the topic for your next thred...... Is a 15feet screen height safe on a wet runway?

It was fun.... thanks..

Mutt
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Old 20th May 2008, 17:00
  #70 (permalink)  
ssg
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Good Questin...Airfoil

If post V1, you have a problem, prior to rotation...you see 8000 feet left, a 1000 ft stopway, and Iowa corn fields beyond...In just about all GA planes including large corporate jets, the question of being able to stop is moot...yes you can...

The question to fly your burning wreck up into the clouds under these circumstances is also moot..you don't do it...

---
After days of arguing with posters on the mertis of post V1 aborts, it turns out I was right...please see SR71s Boeing link on the 'would you abort after V1thread' . I owe SR71 lunch and my sanity..

There is a concept of Min and Max V1s, which will lead to an excellent discussion I think..

Turns out my method of simply 'looking out and seeing if I have enough runway to stop' post V1, has been mathematicaly figured out my Boeing.

On a long runway, in our plane, we could say rotate at 3000 ft and 95 kts.... or you chose to stay on the ground, and continue to accelerate, there is a place, way down farther on the runway, at a certain speed at which you need to start slowing down, inorder to stop before the end of the runway.. this is a v speed like any other... That could be 10000ft and at a speed of 160kts...that could be a V1max...but not technicaly as it's after VR, but for the purposes of stopping, this is the last place on the runway, at a certain speed to do it...

So I will crown a new v speed..the last chance to stop the aircraft after Vr...: Vssg.



In a small plane, they can rotate, take off, land, do it a couple of times before running out of runway..in a small jet, maybe twice...and how do they do this...'hey george...got enough runway infront of us...looks good to me' an they do it...

So here is the Flex or reduced thrust problem....

So now we are sitting here with all this runway infront of us...tons of room to stop...balanced field is 5000ft on a 12000 ft runway..lots of margin for a post V1 stop, lost of safety.....and someone says..

'Let's try to baby the engines today...use reduced power on take off...with the new settings balanced field is now 10000 feet. Let's go.'

So the plane burns up 7000ft, V1...go...just prior Vr, which would be around 10000 ft....both Thrust reversers pop out..11000 ft, pilot realizes he can't fly with both TRs out, pulls the levers 12000ft...he barrels into the corn field..houses, hotel. ect...

He did everything right on that flight, he had the numbers, he was trying to save money, ..everyone is dead...

Had he chosen not to use Flex, or reduced thrust, and hit VR with a TR problem at 5000 ft, he would have made it...7000 ft to slow the plane down...

If on a thousand flights in a year this operator had chosen not to burn up every available ft of runway, every time he took off, to save a buck on engine maintanance, and use up all his margin of safety...how much safer would that be?
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Old 20th May 2008, 17:13
  #71 (permalink)  
 
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Why is the argument ended SSG? Just because there is a range of V1s, there is still only one V1 used during a takeoff. If in your opinion the aircraft is unflyable V1 is irrelevant anyway.
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Old 20th May 2008, 19:14
  #72 (permalink)  
 
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ssg

V1min, Vmax and V1 balanced are not news to most of us! They were to you half way through your discourse.


Now tell me, on any given day do you know which was used in your calculation?

Those of us who use (or produce) runway analysis on a daily basis can find it in the header on most types.

However, we do not see the the options not used in the calculation. The choice is made by company ops and perf departments based on statistical data and analysis of each runway.

If your company would prefer to bias engine failures to be above V1 and so take them airborne they will use V1min. If their are obstacles that limit your take off perf you may wish to use a high V1 thus giving better climb perf but biasing towards more stops.

Statistics show stopping in big jets is less safe so many if not most large companies prefer low V1s.

However if V1min is used the crew are not presented with V1 max or balanced or any other choices.

The reason for not presenting a range of speeds is that at the moment of failure during a take off the crew need to act, not think about whether or not to act. The thinking time is included in the V1 calculation. It is the time between Vef and the first action to stop at V1. This time can vary depending on the certification standards used and systems fitted.

Now your moving goalposts in the previous thread stated with a very simple question. In the case of an engine fire would you stop after V1. The correct answer to that question in NO.

To the question would you ever try to stop after V1 the answer is yes. But the reasons would need to be compelling.

Most runway analysis indicate what is the limiting factor for the take off and as long as it isn't field length OEI or VMBE there is some chance of stopping but that chance diminishes with every nano second you think about doing it.

When we think about using less than rated thrust it is because we accept that there is a maximum take off weight we are certified to use with rated thrust and our current weight is less than that.

If we are prepared to take off at max take off weight there is no argument against taking off with the lowest thrust allowed when we are below max take off weight.

In fact the latter is safer than the former for many reasons.

And it saves a lot of money, which makes our companies profit, which they pass on to us in pay scales, which we use to buy books about aeroplane performance!!!!!!!


end of.
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Old 20th May 2008, 19:59
  #73 (permalink)  
 
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Ssg there are also some aerodynamic safety benefits to using reduced thrust---what are they?----why?
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Old 20th May 2008, 21:05
  #74 (permalink)  
 
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Noise reduction is an aerodynamic benefit

btw: VMCG doesn't necessarily become lower depends on what's written in the TCDS--no? as Chris Scott once 'schooled' me on the airbus and on that type as well as a Vmcg is fixed therefore it would be a benefit---on a new [with the appropriate data] Boeing No ---it can change with a DERATE!!!
unless you know everything about a type never second guess performance

and 150 knots is not the time to be in the charts


me haces muy cansado---ay
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Old 20th May 2008, 21:08
  #75 (permalink)  
ssg
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.....

And the 'unoffical' benefit is?
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Old 20th May 2008, 21:41
  #76 (permalink)  
 
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When you pick your limiting temp---did you just trick the atmosphere too? the airfoils? is reverse thrust also lowered to the assumed temp [unofficial]? had the PA/DA actually changed?


now you can tell me the benefit you are a CFI-no?


PA
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Old 20th May 2008, 21:58
  #77 (permalink)  
 
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Increasing ground roll, decreasing stop distances, decreasing reaction times to a crisis in furthurance of saving a buck on overhaul 5 years later seems counter intuitive...especialy with 200 people in the back....
The thing is, for us it is indeed years later. For your airplane operated to the same standards and usage as an airliner it would be twice a year since we actually use our airplanes to do what they were build for, flying. We have to use our aircrafts (and their engines) up to way over 6000 hours a year, with an overhaul interval of 3500 hours that you apparently need because your engines run out of limit that fast (i wonder why) we would have to keep around one extra pair of engines in the shop per every two airplanes just to keep them flying, and that would need around 7 to 20 million bucks (depending on type) of additional investment just for a pair of them.
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Old 20th May 2008, 22:04
  #78 (permalink)  
ssg
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.......

PA: So what your saying is that the aerodynamic benefit to flex is picking your own limiting temp? Next!
------------------------
Denti, if you and I bought our first old trashed 737 and tried to make a go of a single jet airline, our own money on the line..do or die..sure save a buck anywhere we can but be legal about it...no problem...now flash forward, billions of dollars later, hundreds of new planes on the line, we have something to lose, ..why push the safety envelope at that point....greed?
I am curious what is the WE have to pay for engines, unless you own the airline, your an employee, and management is not on yourside. You know besides mismanagement, a plane crash is pretty much the only single event that can literaly take down an airline and a company..why risk it...

Besides cutting corners on maintanance, I can't see a more dangerous policy at an airline then to tell all the crews to burn up more runway, to cut it closer to the fence...that just asks for trouble.

Last edited by ssg; 20th May 2008 at 22:15.
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Old 20th May 2008, 22:09
  #79 (permalink)  
 
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NO!--that's how you do the procedure
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Old 20th May 2008, 23:04
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better actual acceleration lift changes with acceleration=more lift with given unit time/distance-- the wings are working at a lower pressure altitude because the temp is only 'assumed' for the engines, but the engineers don't take that benefit in account and it gives a margin---

And better stopping [before V1]with reverse becasue you get full rated RT [that's why it unofficial because in part 25 dry RT doesn't exist,]also spoilers and retardation devices are better in the denser air



SNS3Guppy do you see why I said "you gotta wash'em out in ground school"?
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