Cirrus down enroute to OSH

AcroBoy

AcroBoy

Line Up and Wait
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Jul 18, 2008
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Jim N
Yesterday an SR-22 crashed in front of a group of planes and pilots on the way to OSH at the Watertown airport, one of our local uncontrolled fields. By all accounts (mostly pilots), the plane had power when it crashed. Both of the people on board survived with injuries. Let's all be careful out there, especially those going to OSH.
 
Folks, be very careful around Cirrus and other BRS-equipped airplanes after an accident. The sabot that pulls the chute out leaves at 10,000 feet per second. If you get hit, IT WON'T BUFF OUT.

It's a rocket, so it will ignite, and the difference between a solid rocket fuel and an explosive is only interesting to chemists and demo folks. And it's self oxidizing - so once it's lit, it STAYS lit.

Cirrus has a very good course for first responders on how to safe the rocket and other precautions. Highly recommended.
 
i wonder if that will require an engine teardown and inspection?

those Cirri dont usually have much left of them after the fire, thats for sure.
 
tonycondon said:
i wonder if that will require an engine teardown and inspection?

those Cirri dont usually have much left of them after the fire, thats for sure.
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Is the prop also composite? I don't see a sign of one ever been installed so did it melt, too?
 
TMetzinger said:
Folks, be very careful around Cirrus and other BRS-equipped airplanes after an accident. The sabot that pulls the chute out leaves at 10,000 feet per second. If you get hit, IT WON'T BUFF OUT.

It's a rocket, so it will ignite, and the difference between a solid rocket fuel and an explosive is only interesting to chemists and demo folks. And it's self oxidizing - so once it's lit, it STAYS lit.

Cirrus has a very good course for first responders on how to safe the rocket and other precautions. Highly recommended.
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Good advice, Tim. Sounds like the main danger from a fire would be shrapnel--it won't launch the sabo. The following is from page 9 of the document you referred to above:

http://brsparachutes.com/ViewDocument.aspx?DocumentID=34 said:
A rocket motor that has separated from the igniter poses no significant hazard, unless it is exposed to fire. Experience has shown that a rocket motor subjected to high temperatures (fire) will not ignite in a normal manner and launch. Rather, they have been observed to burst in a relatively non-threatening display.
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I suppose it's possible, but 10,000fps sounds really high, since most high powered rifles have a muzzle velocity in the range of 3500fps. Most composite props are largely made of wood laminates, so would more likely burn than melt. Regardless, the people on board were lucky to survive. The MJS article was pretty factual rather than including the usual inaccurate speculations seen in the media.
 
OK I read the article and still do not get it.

Were they landing and he tried to force it down?

Or was the DA really high and he tried to force it in the air?
 
My read is, he came in hot, tried to force it down, and aborted the landing too late to go around successfully.

Thank God they are (relatively) alright, and that no one else was killed or injured.

---

Also, from the same article, I am a little surprised to read that the PA24 is in its fiftieth year of manufacture!
 
TMetzinger said:
Cirrus has a very good course for first responders on how to safe the rocket and other precautions. Highly recommended.
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I read it last week, its here:
http://brsparachutes.com/ViewDocument.aspx?DocumentID=34
Honestly I didn't find it that simple. I think if I was near a wrecked Cirrus I would just tell people to stay the h away from the direction that thing shoots! (you need special wire cutters to snip the cable and housing. they recommend against bolt cutters etc)
 
I just wrapped up an IR stage check yesterday at KUES, and when I walked into the FBO the news was about the crash. Watertown is a nearby airport that we frequent, so I called my wife to let her know that it wasn't us.

Hopefully that couple will heal. The plane can be replaced. Thank goodness no one on the ground was injured.
 
AcroBoy said:
I suppose it's possible, but 10,000fps sounds really high, since most high powered rifles have a muzzle velocity in the range of 3500fps. Most composite props are largely made of wood laminates, so would more likely burn than melt. Regardless, the people on board were lucky to survive. The MJS article was pretty factual rather than including the usual inaccurate speculations seen in the media.
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Dude, it's a ROCKET.
 
TangoWhiskey said:
Good advice, Tim. Sounds like the main danger from a fire would be shrapnel--it won't launch the sabo. The following is from page 9 of the document you referred to above:
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It doesn't launch if it's outside it's shell. But it does burn, quickly, energetically, and you can't put it out with water or foam.

If it's still in the shell, high temps can cook off the igniter (sort of an empty shotgun shell), and that would launch the rocket.

Also, keep in mind that different airplanes have different propellant loads since they have to launch different parachute payloads.
 
According to what I saw on the web site, the rocket is initially 100mph for just under a second.

Q. What happens after I pull the handle?
A. In the first 0.1 second, the rocket accelerates to 150 feet per second (over 100 mph). In less than one second, the rocket will extract the parachute and will stretch tight its lines and the airframe harness attachments. Very shortly afterward -- depending on the forward speed of the aircraft -- the canopy will become fully inflated and will decelerate the aircraft. The aircraft stabilizes under the canopy quite quickly.
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The document for emergency services personnel doesn't state the total firing period but it appears to be well under one second. It will slow down rather rapidly after that. There's nothing on the web site I can find to indicate it's absolute fastest speed during firing.

I'd think they would want the firing time only long enough to extract the chute and no longer as that could over-stress the lines.
 
100mph sounds more reasonable to me. I think Mach 10 would make it faster than even stuff like the space shuttle.
 
Mea Maxima Culpa... I just went through the notes I took at the course. 10000 feet per MINUTE, and that's the initial velocity. When it takes up the load of the chute, of course, it's slows down a lot.

They had one go off with the sabot NOT attached to the chute - Sabot went up above 10000 feet.

Thanks for the argument. Always good to be corrected when in error.
 
Great reply- it's not like the rest of us have ever been wrong before either! Went flying today just to do some casual acro over our box, but there were some many traffic alerts with OSH bound traffic that I decided to bag it as being too dangerous. Came back and washed the plane instead.
 
TMetzinger said:
Dude, it's a ROCKET.
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Tim, I didn't sit down with a calculator, but my little head tells me that's somewhere around mach 9. An AIM-9 only makes about 2.5. :dunno:

Oops, just went ahead and read posts following the one I answered. Sorry about that. :D
 
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AcroBoy said:
Great reply- it's not like the rest of us have ever been wrong before either! Went flying today just to do some casual acro over our box, but there were some many traffic alerts with OSH bound traffic that I decided to bag it as being too dangerous. Came back and washed the plane instead.
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I was wondering that yesterday when I was on an IR stage check in the NW practice area of KUES. We were at 3-5,000 ft and I was wondering what might be flying by as I was under the hood.:hairraise:

As for the accident, I just heard on local news that interviewed resident pilots at Watertown (KRYV) that the Cirrus pilot hangared his aircraft at that airport. They also said that he has been flying for two years.
 
2256Q said:
Tim, I didn't sit down with a calculator, but my little head tells me that's somewhere around mach 9. An AIM-9 only makes about 2.5. :dunno:

Oops, just went ahead and read posts following the one I answered. Sorry about that. :D
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And all of you wise guys failed to note that the Mach number depends on the density altitude. :rolleyes:
 
tonycondon said:
it does?

sqrt(gamma*R*T)

where's DA in that?
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OK, wiser guy (Geez. College kids) is there a difference between Mach number and "The speed of sound?" because I always heard that the location of the "sound barrier" depends on altitude, ie. the density of the air.
 
mach number is just:

your speed / speed of sound

speed of sound for an ideal gas is based on temperature.
 
tonycondon said:
mach number is just:

your speed / speed of sound

speed of sound for an ideal gas is based on temperature.
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Yeahbut the speed of sound is not constant. Consider that the speed of sound at 300,000 feet is never, :D, as in sound doesn't travel, so your Mach number has to go to infinity.

I used to think that the speed of sound was like 600-700-something MPH, but I was told it varies with altitude.
 
mikea said:
Yeahbut the speed of sound is not constant. Consider that the speed of sound at 300,000 feet is never, :D, as in sound doesn't travel, so your Mach number has to go to infinity.

I used to think that the speed of sound was like 600-700-something MPH, but I was told it varies with altitude.
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well obviously there needs to be some sort of gas available for the ideal gas assumption to still apply.

and your 6-700 mph figure is about right. and in the standard atmosphere the speed does change with altitude. in fact it varies directly with the standard temperature at the specified altitude.
 
mikea said:
OK, wiser guy (Geez. College kids) is there a difference between Mach number and "The speed of sound?" because I always heard that the location of the "sound barrier" depends on altitude, ie. the density of the air.
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At sea level on the so-called standard day, speed of sound is approximately 763 mph. At 35 or 40 thousand feet, it drops to approximately 663 mph. That's off the top of my head from USAF training. Please don't make me look it up. :)
 
you have better memory than me Ray. I gave up on trying to remember specific numbers a long time ago and just stuck with formulas!
 
tonycondon said:
you have better memory than me Ray. I gave up on trying to remember specific numbers a long time ago and just stuck with formulas!
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It was just something they jammed down our throats. I never quite understood why, since the mach meters worked just fine. I think it was probably a leftover from the days when they had tail flutter problems in the trans-sonic regions. They did a good job of fixing that, though, and without instrumentation, a pilot never knows when the plane goes supersonic.

Well, almost never. :)
 
mikea said:
OK, wiser guy (Geez. College kids) is there a difference between Mach number and "The speed of sound?" because I always heard that the location of the "sound barrier" depends on altitude, ie. the density of the air.
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Mike, the Mach number is already adjusted before you see it on the gauge. A mach indication of .9 at 1,000 feet versus .9 at 40,000 feet are both .9 mach. The difference is that the speed will be something else.
 
jesse said:
Mike, the Mach number is already adjusted before you see it on the gauge. A mach indication of .9 at 1,000 feet versus .9 at 40,000 feet are both .9 mach. The difference is that the speed will be something else.
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Ahhhh, OK gotcha. It's like true vs. calibrated airspeed.
 
2256Q said:
At sea level on the so-called standard day, speed of sound is approximately 763 mph. At 35 or 40 thousand feet, it drops to approximately 663 mph. That's off the top of my head from USAF training. Please don't make me look it up. :)
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At the tropopause the temperature starts to rise with altitude and the speed of sound starts to rise again, too. Temperature is the factor.
This is one of those things that's not intuitive; we tend to think "density" because sound travels faster in water or steel, both denser than air.

http://www.sengpielaudio.com/SpeedOfSoundPressure.pdf
http://www.aerospaceweb.org/question/atmosphere/q0112.shtml

Dan
 
Dan Thomas said:
At the tropopause the temperature starts to rise with altitude and the speed of sound starts to rise again, too. Temperature is the factor.
This is one of those things that's not intuitive; we tend to think "density" because sound travels faster in water or steel, both denser than air.

http://www.sengpielaudio.com/SpeedOfSoundPressure.pdf
http://www.aerospaceweb.org/question/atmosphere/q0112.shtml

Dan
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Been a while since I studied it, but doesn't that temp rise start way up above where it would affect any air-breathing engine?
 
First glad to here they made it out.
With all the pilots around why did they have to get there quote from the mail carrier? It will be intersting what the FAA will have to inspect. Not much of the plane left.
 
2256Q said:
Been a while since I studied it, but doesn't that temp rise start way up above where it would affect any air-breathing engine?
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Depends where you are, latitude wise as well as seasonal-wise. Here in Canada the tropopause is found around the 30,000-foot level in the winter, maybe 40,000 or a little higher in the summer. Many bizjets and a few of the newer airliners can fly well above that. At the equator, IIRC, the tropopause is consistently around 60K.
See http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/tropo.html

Dan
 
Dan Thomas said:
Depends where you are, latitude wise as well as seasonal-wise. Here in Canada the tropopause is found around the 30,000-foot level in the winter, maybe 40,000 or a little higher in the summer. Many bizjets and a few of the newer airliners can fly well above that. At the equator, IIRC, the tropopause is consistently around 60K.
See http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/tropo.html

Dan
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Actually, I was thinking about the point where the temp starts to rise toward some unbelievable figure, like 2,500 degrees or some such. Seem like it was back to about the same as sea level about the time you got to 100,000 feet or so, and began climbing sharply after that as altitude increases.
 
at those altitudes it gets a little tricky to really determine temperature because there just arent that many molecules to bump into each other.
 
tonycondon said:
at those altitudes it gets a little tricky to really determine temperature because there just arent that many molecules to bump into each other.
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I'm remembering this from the old NASA days, Tony. It was something we had to deal with on the space shots. No really big deal, just something to consider in calculations. The temp gets pretty darned hot once you get on up there a few hundred thousand feet.
 
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