NWADC9
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What's So Special About 10,000 Feet?

Mon Sep 28, 2009 8:03 pm

The 250kt. restriction ends. Personal electronic devices may be used. Why do these things begin at 10,000 feet? What's so special about that altitude?
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OPNLguy
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 8:12 pm

FAA considers airline ops below 10,000 as critical safety of flight territory.. Portable electronic devices, sterile cockpit, the 250 KIAS limit, exposure to GA aircraft that are not oxygen-equipped --those are just four examples.

[Edited 2009-09-28 13:25:20]
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
BMI727
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 8:16 pm

It is just that pretty much any problem is magnified when you are closer to the ground. Being above 10,000 feet there is more margin for error and the crew can "relax" a bit.

Quoting NWADC9 (Thread starter):
The 250kt. restriction ends.

Usually when planes are below 10,000 they are, of course, near airports. This rule helps keep things from moving too quickly for the controllers and helps put everyone on a level playing field which helps ease sequencing a little bit. I believe that certain airports have their own speed restrictions for certain flight paths to further help in this respect. Also, the rule actually says 250 kts or the aircraft's minimum clean speed, whichever is higher.

Quoting NWADC9 (Thread starter):
Why do these things begin at 10,000 feet?

You forgot that 10,000 feet is usually also the ceiling of the sterile cockpit rule, for the same reasons as above.
Why do Aerospace Engineering students have to turn things in on time?
 
IAHFLYR
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 8:26 pm



Quoting BMI727 (Reply 2):
This rule helps keep things from moving too quickly for the controllers and helps put everyone on a level playing field which helps ease sequencing a little bit

Really! What brings you to that conclusion? Is it so the B739 which slows to 250 KIAS won't catch the110 KIAS C172 on approach?
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BMI727
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 8:28 pm



Quoting IAHFLYR (Reply 3):
Really! What brings you to that conclusion? Is it so the B739 which slows to 250 KIAS won't catch the110 KIAS C172 on approach?

Which is why I said "helps." All of the jets are doing the same speed roughly, and they make up the bulk of the flights at major airports. And if you think that is bad, just imagine the headaches if your 737 was doing 300+.
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mrskyguy
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 8:31 pm

Old salt pilots used to call this zone (0-10,000' MSL) "Indian Territory" due to the number of GA pilots which operate in VFR conditions (Indian = Piper named most/all? of their aircraft after Native American tribes).

I always found that little peice of trivia interesting.
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ThrottleHold
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 8:42 pm



Quoting BMI727 (Reply 4):
And if you think that is bad, just imagine the headaches if your 737 was doing 300+.

The rest of the world copes alright! I remember doing 350 Kts at 2000ft in a B747 on the way into Frankfurt.
 
IAHFLYR
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 8:45 pm



Quoting BMI727 (Reply 4):
And if you think that is bad, just imagine the headaches if your 737 was doing 300+.

Funny you should mention that.....they'd actually get out of your hair faster.  Smile
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Pacific
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 9:19 pm



Quoting ThrottleHold (Reply 6):

http://aviation-safety.net/database/record.php?id=19670309-0

Quote:
Following this accident the FAA issued Advisory Circular 90-32 titled 'Air traffic control and general operations, radar capabilities and limitations'. Also a rule was adopted establishing that all aircraft flying below 10,000ft msl will be limited to a maximum speed of 250kts effective December 15, 1967 to provide a more realistic 'see and avoid' environment.

 
lowrider
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 9:40 pm



Quoting ThrottleHold (Reply 6):
The rest of the world copes alright! I remember doing 350 Kts at 2000ft in a B747 on the way into Frankfurt.

Most of the rest of the world does not have the GA environment that the US does. Canada is a notable exception. Even many European airports have speed limit points on the arrivals that require you to slow down as you before you cross them.
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KELPkid
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 9:40 pm

Two things I can think of:

#1) the vast majority of GA ops happens at 10,000 feet and below, although some does happen above that. I have cruised high performance singles (and a 180 HP 172  Smile ) at 11,500' and 12,500' before...and I have flown a Cessna 210 at 14,000' on Oxygen (using a portable oxygen system). This was because 14,000' was the MEA on the particular airway we were using down in Mexico...

#2) the FAA regards 10,000' as the highest usable (without restrictions) unpressurized altitude. Above 10,000', FAR restrictions start kicking in...  Wink Also, speed limits and (if you're VFR) visibility requirements change at and above 10,000' .
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Mir
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RE: What's So Special About 10,000 Feet?

Mon Sep 28, 2009 10:31 pm



Quoting IAHFLYR (Reply 3):
Is it so the B739 which slows to 250 KIAS won't catch the110 KIAS C172 on approach?

No, but it does help the 172 see and avoid the 739 when both are in the vicinity of the airport.

Quoting KELPkid (Reply 10):
the FAA regards 10,000' as the highest usable (without restrictions) unpressurized altitude. Above 10,000', FAR restrictions start kicking in...

Which FAR restrictions are those? Last I checked, the lowest altitude for oxygen requirements is 12,500.

-Mir
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spudsmac
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RE: What's So Special About 10,000 Feet?

Tue Sep 29, 2009 1:49 am



Quoting ThrottleHold (Reply 6):

The rest of the world copes alright! I remember doing 350 Kts at 2000ft in a B747 on the way into Frankfurt.

I don't want to be flying in a 172 in echo airspace (where I may fly without talking to anyone!), just climbing through 2000ft and have a 747 come screaming by at 300kias.

Also, correct me if I am wrong, but doesn't positive control airspace (Class Alpha equivalent) start a lot lower in some other parts of the world that may not have this speed restriction? In that case, all the aircraft would be talking to someone and pilots would be vectored out of the way in time.
 
keta
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RE: What's So Special About 10,000 Feet?

Tue Sep 29, 2009 5:46 am



Quoting BMI727 (Reply 2):
This rule helps keep things from moving too quickly for the controllers and helps put everyone on a level playing field which helps ease sequencing a little bit.

I have read that the 250 kt limit was a protection for the flight envelope against birdstrike. What's true about this?
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IAHFLYR
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RE: What's So Special About 10,000 Feet?

Tue Sep 29, 2009 11:13 am



Quoting Keta (Reply 13):
I have read that the 250 kt limit was a protection for the flight envelope against birdstrike

See reply 8, Pacifc posted a link to the "original" reason.

The birdstrike issue is another concern which is aways tossed into the mix, yet in some countries it has not enough an issue for them to slow at 10,000'!
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Illini_152
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RE: What's So Special About 10,000 Feet?

Tue Sep 29, 2009 9:20 pm



Quoting Mir (Reply 11):

Which FAR restrictions are those? Last I checked, the lowest altitude for oxygen requirements is 12,500.

§ 135.89 Pilot requirements: Use of oxygen.

(a) Unpressurized aircraft. Each pilot of an unpressurized aircraft shall use oxygen continuously when flying—

(1) At altitudes above 10,000 feet through 12,000 feet MSL for that part of the flight at those altitudes that is of more than 30 minutes duration; and

(2) Above 12,000 feet MSL.

(b) Pressurized aircraft. (1) Whenever a pressurized aircraft is operated with the cabin pressure altitude more than 10,000 feet MSL, each pilot shall comply with paragraph (a) of this section.

(2) Whenever a pressurized aircraft is operated at altitudes above 25,000 feet through 35,000 feet MSL, unless each pilot has an approved quick-donning type oxygen mask—

(i) At least one pilot at the controls shall wear, secured and sealed, an oxygen mask that either supplies oxygen at all times or automatically supplies oxygen whenever the cabin pressure altitude exceeds 12,000 feet MSL; and

(ii) During that flight, each other pilot on flight deck duty shall have an oxygen mask, connected to an oxygen supply, located so as to allow immediate placing of the mask on the pilot's face sealed and secured for use.

(3) Whenever a pressurized aircraft is operated at altitudes above 35,000 feet MSL, at least one pilot at the controls shall wear, secured and sealed, an oxygen mask required by paragraph (b)(2)(i) of this section.

(4) If one pilot leaves a pilot duty station of an aircraft when operating at altitudes above 25,000 feet MSL, the remaining pilot at the controls shall put on and use an approved oxygen mask until the other pilot returns to the pilot duty station of the aircraft.
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BMI727
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RE: What's So Special About 10,000 Feet?

Tue Sep 29, 2009 9:42 pm



Quoting Keta (Reply 13):
I have read that the 250 kt limit was a protection for the flight envelope against birdstrike. What's true about this?

It is certainly a benefit, but I don't know if that is why the rule was enacted. I do know that some birdstrikes occur as high as 30,000.
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Mir
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RE: What's So Special About 10,000 Feet?

Tue Sep 29, 2009 10:43 pm



Quoting Illini_152 (Reply 15):
§ 135.89 Pilot requirements: Use of oxygen.

Fair enough. I'm not familiar with 135 regs.

-Mir
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Braniff747SP
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RE: What's So Special About 10,000 Feet?

Wed Sep 30, 2009 11:36 pm

But why the electric stuff rule at 10K??


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PGNCS
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RE: What's So Special About 10,000 Feet?

Thu Oct 01, 2009 2:00 am



Quoting ThrottleHold (Reply 6):
The rest of the world copes alright! I remember doing 350 Kts at 2000ft in a B747 on the way into Frankfurt.

I wish you luck when you hit a goose.
 
jeffry747
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RE: What's So Special About 10,000 Feet?

Fri Oct 02, 2009 9:14 pm

The other day I flew SDF-CVG in an EMB-145. According to FlightAware.com, we cruised at 9,000ft and 286kts. I am pretty sure the minimum clean speed of the EMB-145 is less than 250kts. How is it we were allowed to go faster than the speed limit below 10k ft. Is it legal?
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2H4
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RE: What's So Special About 10,000 Feet?

Fri Oct 02, 2009 9:18 pm



Quoting Jeffry747 (Reply 20):
According to FlightAware.com, we cruised at 9,000ft and 286kts.

Two thoughts:

- As great a site as FlightAware is, I'd be careful not to overestimate the accuracy of its data
- Flightaware records groundspeed. Not indicated airspeed.

2H4
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9VSIO
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RE: What's So Special About 10,000 Feet?

Fri Oct 02, 2009 10:34 pm

UK has a limit of 250 below 10k, but I believe ATC can remove that restriction.
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zappbrannigan
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RE: What's So Special About 10,000 Feet?

Sun Oct 04, 2009 6:13 am



Quoting Spudsmac (Reply 12):
I don't want to be flying in a 172 in echo airspace (where I may fly without talking to anyone!), just climbing through 2000ft and have a 747 come screaming by at 300kias.

Also, correct me if I am wrong, but doesn't positive control airspace (Class Alpha equivalent) start a lot lower in some other parts of the world that may not have this speed restriction? In that case, all the aircraft would be talking to someone and pilots would be vectored out of the way in time.

Is that possible in the US? Here in Aus, Class E airspace doesn't exist anywhere below 8,500', and generally steps up to a lower limit of FL180, above which is Class A.

Until you hit some Class E departing a major aerodrome, all airspace is either Class G unrestricted, or Class C above the Class G. VFR aircraft operating in Class E airspace do not require a clearance, but do require a Mode-C transponder operating - meaning the chances of coming across a random 747 are pretty low. And this can't happen at 2,000' here. A slightly higher risk is the IFR aircraft maintaining 10,000 flying head-on with the VFR aircraft at 9,500 in Class E, and the controller trying to sort it out, as has happened to me a few times - although this is no different to the same thing in unrestricted airspace. The big jets are kept well clear.

Our Class A doesn't exist below FL180 anywhere.
 
lowrider
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RE: What's So Special About 10,000 Feet?

Sun Oct 04, 2009 11:30 am



Quoting Zappbrannigan (Reply 23):
Is that possible in the US?

Yes. Many parts of the country, class E may start as low as 700 ft agl. At many small airports served by instrument approaches, it goes down to the surface so as to protect the area needed to conduct the approach during IFR ops. If there is no airway, transition, approach, or airport requirement, it may start aa high as 14,500.

Quoting Zappbrannigan (Reply 23):
all airspace is either Class G unrestricted

Our class G is designated uncontrolled, and starts at the surface and may go as high as 14,500.

Quoting Zappbrannigan (Reply 23):
Class C

Class B, C, and D are all associated with airport and a portion surrounding the airport will go to the surface. All of class D goes to the surface.

Quoting Zappbrannigan (Reply 23):
Our Class A doesn't exist below FL180 anywhere.

Nor does ours.
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9VSIO
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RE: What's So Special About 10,000 Feet?

Sun Oct 04, 2009 10:22 pm



Quoting Zappbrannigan (Reply 23):

The UK has plenty of class A airspace at lower altitudes. In fact, it can be extremely trying to navigate between the huge chunks of controlled airspace. Just check out the LTMA for lots of Class A!
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zappbrannigan
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RE: What's So Special About 10,000 Feet?

Mon Oct 05, 2009 12:52 am



Quoting Lowrider (Reply 24):
Yes. Many parts of the country, class E may start as low as 700 ft agl. At many small airports served by instrument approaches, it goes down to the surface so as to protect the area needed to conduct the approach during IFR ops. If there is no airway, transition, approach, or airport requirement, it may start aa high as 14,500.

Interesting. Class E here only serves higher-capacity airports - 98% of the airports here which have published approaches are in Class G airspace, and only IFR traffic information is provided by ATC (no separation). If you're conducting an approach, ATC will have passed to you the details of all reported/observed IFR traffic (plus any VFR in the area they have on radar) but will not provide any separation, and you'll get no control area protection of any kind.

Many of our small airports, especially in the top end of Aus, are outside radar coverage so ATC are relying on position reports from IFR aircraft to provide traffic information - and of course this is all Class G. I imagine the scale of radar and ATC in the US is hugely greater than ours, so control services and Class E services can actually be provided at small airports.
 
hotelmode
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RE: What's So Special About 10,000 Feet?

Mon Oct 05, 2009 8:46 pm



Quoting Jeffry747 (Reply 20):
we cruised at 9,000ft and 286kts. I am pretty sure the minimum clean speed of the EMB-145 is less than 250kts. How is it we were allowed to go faster than the speed limit below 10k ft. Is it legal?

Doesnt flight aware use groundspeed or at least true air speed? 240 kts indicated air speed is roughly 286 kts TAS or groundspeed at 9000ft anyway. An airframe speed restriction is based on indicated airspeed.
 
IAHFLYR
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RE: What's So Special About 10,000 Feet?

Tue Oct 06, 2009 2:24 am



Quoting Hotelmode (Reply 27):
Doesnt flight aware use groundspeed or at least true air speed? 240 kts indicated air speed is roughly 286 kts TAS or groundspeed at 9000ft anyway.

And don't forget, groundspeed also includes the winds aloft in the total number.

Quoting Lowrider (Reply 24):
Class B, C, and D are all associated with airport and a portion surrounding the airport will go to the surface. All of class D goes to the surface.

Class E also goes to the surface.
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Mir
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RE: What's So Special About 10,000 Feet?

Tue Oct 06, 2009 2:32 am



Quoting Jeffry747 (Reply 20):
The other day I flew SDF-CVG in an EMB-145. According to FlightAware.com, we cruised at 9,000ft and 286kts. I am pretty sure the minimum clean speed of the EMB-145 is less than 250kts. How is it we were allowed to go faster than the speed limit below 10k ft. Is it legal?

Flightaware looks at groundspeed (as does ATC). 286kts sounds about right for 250kias at that altitude.

Quoting Zappbrannigan (Reply 23):
Is that possible in the US? Here in Aus, Class E airspace doesn't exist anywhere below 8,500'

In the US, Class E generally starts at 1200' AGL. Sometimes it will start at 700' AGL or at the surface, depending on the need for IFR separation in very marginal conditions (the weather minima are lower for E than for G, so you can avoid a situation where an aircraft is flying VFR in 1sm vis and clear of clouds as another aircraft is IFR on an approach to the airport (a nice recipe for a mid-air) by dropping the floor of Class E down so that the VFR aircraft wouldn't be allowed to fly there under those conditions.

Out in the more deserted parts of the US (in the western states), Class E will sometimes start at 14,500' MSL.

-Mir
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IAHFLYR
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RE: What's So Special About 10,000 Feet?

Tue Oct 06, 2009 2:39 am



Quoting Mir (Reply 29):
Flightaware looks at groundspeed (as does ATC). 286kts sounds about right for 250kias at that altitude.

Oh come on Mir, don't tell the public that ATC looks at groundspeeds.........dang it!!!  eyepopping 

Quoting PGNCS (Reply 19):
I wish you luck when you hit a goose.

Just curious, how many have you hit in the air and how many total hours do you have?
Any views shared are strictly my own and do not a represent those of any former employer.
 
lowrider
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RE: What's So Special About 10,000 Feet?

Tue Oct 06, 2009 5:22 am



Quoting IAHFLYR (Reply 28):
Class E also goes to the surface.

If you could be bothered to read to the second sentence you would have seen...

Quoting Lowrider (Reply 24):
At many small airports served by instrument approaches, it goes down to the surface so as to protect the area needed to conduct the approach during IFR ops.

Proud OOTSK member
 
IAHFLYR
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RE: What's So Special About 10,000 Feet?

Tue Oct 06, 2009 11:33 am



Quoting Lowrider (Reply 31):
If you could be bothered to read to the second sentence you would have seen...

Excuse me, what was I thinking other than the fact I wasn't referencing the same paragraph as you indicate.
Any views shared are strictly my own and do not a represent those of any former employer.
 
mpdpilot
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RE: What's So Special About 10,000 Feet?

Thu Oct 15, 2009 4:35 am

I thought I would share my understanding of the 10,000' significance.

There are some rather significant atmospheric changes that occur above 10,000'. You can see this with a lot of GA aircraft with service ceilings right around 10,000'. Not to mention the pressure change at that altitude. Also to quote the FAR's 91.211 it is 12,500' and above where the oxygen requirements come to play for most general aviation flying.

With this most general aviation flying occurs below 10,000'. In an effort to keep things at the very least closer to each other aircraft are restricted to speed of 250KTS or slower. It is for that same reason that there is a 200KTS requirement in class D airspace and underneath class B airspace.

With the slow down and increase traffic comes the increase vigilance required by flight crews, hence the sterile cockpit rule. Also with this increased traffic requires increased navigation performance and all around more accurate flying, hence the ban on electronic devices that may interfere with these systems.

Now could this be changed to 12,000' probably, could this also be 9000' sure. I would say that in addition to numerous atmospheric changes at 10,000', 10,000' was chosen because of the roundness of the number. Very easy to remember and just a good reference point.

So as you can see there are a number of things that go together to make the magic number 10,000'
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ferrypilot
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RE: What's So Special About 10,000 Feet?

Mon Oct 19, 2009 11:08 pm



Quoting PGNCS (Reply 19):
I wish you luck when you hit a goose.

Just as a matter of interest do you happen to know if your windscreen would deflect a Goose at 250knots.
 
IAHFLYR
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RE: What's So Special About 10,000 Feet?

Mon Oct 19, 2009 11:13 pm



Quoting Ferrypilot (Reply 34):
Just as a matter of interest do you happen to know if your windscreen would deflect a Goose at 250knots

A question that I've asked a few times and even a time or two on this site, still waiting to hear the answer if anyone does know?
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