What is your TOSA today?

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JohnnyHotRocks
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What is your TOSA today?

#1 Post by JohnnyHotRocks » Thu Nov 16, 2017 7:05 pm

After a stimulating simulator conversation, I would like to get an idea of what everyone is using for TOSA.
400agl? 1500agl? Other numbers?
What about in unfamiliar terrain?

Let the arguments begin!
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Re: What is your TOSA today?

#2 Post by Jet Jockey » Fri Nov 17, 2017 7:36 am

The 400' AGL is a minimum I believe from standards established in aircraft certification dating way back and should be seen as a "minimum" level off altitude.

This said it all depends how old your aircraft is and how it was certified at the time. How was the AFM's performance data was published and approved.

The type of aircraft you fly; piston, turboprop or jet, will also have an impact on your level off altitude. I would not expect a pilot flying a Piper Navajo to wait until 1500' AGL to start his emergency drills in case of an engine failure (he'd never make it there).

Some aircrafts have a level off as low as 400' AGL up to 1500' AGL or until a maximum time of 5 minutes. Some AFM's allow for short in or close by obstacles which may take you past a 1500' AGL level off (extended second climb gradient).

In our everyday operation (jets) if we are not obstacle limited we will do our level off at 1500' AGL (never 400' AGL).

However we do use "runway analysis" for every airport we fly in and out of and will adjust or level off accordingly which is generally 1500' AGL but in mountainous regions like KEGE or KASE just to name two the level offs could be higher than 1500' AGL.
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Re: What is your TOSA today?

#3 Post by confusedalot » Fri Nov 17, 2017 6:48 pm

Waaay back, I recall a ground school lesson, with manufacturer graphs and all, showing distance from liftoff versus altitude, or something like that, it's been a long time.

As I recall, it was pretty much up to the operator, and most importantly, aircraft type, to determine the altitude that they wanted to incorporate into their operations, (400 to 1500 feet)

Worked for an operator doing 400, worked for another doing 1500, but mostly, operators seemed to select 1000 feet for whatever reason, suspect for convenience.

As the OP said, let the games begin! Any performance engineers on the forum?
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Re: What is your TOSA today?

#4 Post by JohnnyHotRocks » Fri Nov 17, 2017 7:24 pm

What I am getting at is, in absence of APG or similarly runway analysis, in an area with terrain above 1500', what would you do?
Where would you look to find a safe acceleration altitude?
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Re: What is your TOSA today?

#5 Post by planett » Fri Nov 17, 2017 7:36 pm

Plan to "scrape the paint". 400 or 35' over the limiting obstacle, net. Any higher is wasteful. Extra safety costs money. Have you ever looked down from a 35' diving board? Too high for me.
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Re: What is your TOSA today?

#6 Post by confusedalot » Fri Nov 17, 2017 8:24 pm

If you are looking for escape routes like some airports in Austria or Switzerland, as an example, as far as I recall, the jepps would publish those as well.

I guess you could do the analysis yourself, but that would be a frustrating experience. Also, in airports like that, the standard IFR plates would most probably give you guidance.
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Re: What is your TOSA today?

#7 Post by wallypilot » Sat Nov 18, 2017 11:50 am

JohnnyHotRocks wrote:
Fri Nov 17, 2017 7:24 pm
What I am getting at is, in absence of APG or similarly runway analysis, in an area with terrain above 1500', what would you do?
Where would you look to find a safe acceleration altitude?
If you don’t have runway analysis, and you need to go in IMC with terrain in your departure path, if you want to be as safe as you could possibly be (legally speaking) you really have no choice but to use MSA. With MSA’s typically much much higher than is really required to clear obstacles, it’s clear why operators incorporate runway analysis into their operations. Using MSA, You will be severely penalized on your take off weight tho, so it might end up being meaningless if you’re just using MSA but not confirming that you can make the climb gradient to get there. Also, with aircraft that have MCT Time limitations, climbing to MSA at MCT or APR may also tigger maintenance inspections. Another reason supporting the use of runway analysis.
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Re: What is your TOSA today?

#8 Post by Ki-ll » Wed Nov 22, 2017 7:10 pm

After doing some research on this I have no idea how it is legal to fly with anything other than runway analysis from guys like APG. The point of regulations is to be at least 35 feet away from any obstacles in the departure path all the way to enroute altitude. Pilots have no idea where these obstacles are, while they are published in various sources, most of these sources are not available to pilots. Even if they would be accessible, to satisfy the regulatory requirements one would have to spend some time with spaghetti charts.
Also, one doesn’t have to be in mountainous terrain to be weight limited. A simple crane protruding into the obstacle clearance envelope close to runway threshold is sufficient to noticeably decrease the take off weight.
As far as original question goes, we get that data from APG performance.
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Re: What is your TOSA today?

#9 Post by wallypilot » Thu Nov 23, 2017 9:18 pm

Ki-ll wrote:
Wed Nov 22, 2017 7:10 pm
After doing some research on this I have no idea how it is legal to fly with anything other than runway analysis from guys like APG. The point of regulations is to be at least 35 feet away from any obstacles in the departure path all the way to enroute altitude. Pilots have no idea where these obstacles are, while they are published in various sources, most of these sources are not available to pilots. Even if they would be accessible, to satisfy the regulatory requirements one would have to spend some time with spaghetti charts.
Also, one doesn’t have to be in mountainous terrain to be weight limited. A simple crane protruding into the obstacle clearance envelope close to runway threshold is sufficient to noticeably decrease the take off weight.
As far as original question goes, we get that data from APG performance.
You are absolutely correct. OP was wondering about in the absence of APG data and alternate departure procedures, and in that case, you’d have to wait until the weather was better to allow you to see and avoid until you get to MSA. I think the OP’s question has merit though from an academic POV.

Without a provided acceleration height, using 2nd segment climb gradient data from the AFM would be the only reference you have to be able to ascertain if you can outclimb terrain. But honestly, for a measly couple grand a year, just get APG people!!
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Re: What is your TOSA today?

#10 Post by Broker » Sun Nov 26, 2017 7:31 am

JohnnyHotRocks wrote:
Fri Nov 17, 2017 7:24 pm
What I am getting at is, in absence of APG or similarly runway analysis, in an area with terrain above 1500', what would you do?
Where would you look to find a safe acceleration altitude?
A sector safe altitude, MEA or a hold at which to either shuttle or execute an emergency approach off.
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Re: What is your TOSA today?

#11 Post by FADEC » Tue Nov 28, 2017 1:12 am

400 ft is the end of second segment climb as defined in Part 25.

So; in the absence of other factors, acceleration can begin at 400 ft AGL.

In the days of Piston Airliners, 400 ft was a long time at gross weight.

For modern aircraft, many operators have moved to higher altitudes, as performance is more assured, and engines more robust.

In a four engine aircraft; one might start letting the speed sneak up to two engine climb speed in the anticipation of another engine failure. (always happens in the Sim for some reason.) Every four engine driver should have that speed hard wired into their brain! For sure; if things are going bad in the real world, and terrain is not a factor, be prepared to lose another engine.

Don't shut down an engine producing power if terrain is a factor. The Concorde crash out of Paris was a classic example; engines shut down prior to safety speed; at that point, physics took over.

Some three engine aircraft are not great on two; such as a 727-200 at gross weight on a hot and high day.

For sure, knowing the terrain or having a good runway analysis beats guessing!
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Re: What is your TOSA today?

#12 Post by goingmach_1 » Mon Jan 08, 2018 9:55 am

Great info here. Sorry cannot link the exact page on the website, but look at:

www.code7700.com

Click on normals, then departure obstacle analysis.

Very in depth.
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