IMPACT OF CABIN PRESSURISATION ABOVE ARMING ALTITUDE ON FUNCTIONALITY OF AADs

[randhawa922 1]

Hello everyone! 
Please throw some light on following questions:

1. What if the cabin is pressurised after climbing & crossing 3000 feet AGL(considering safe margin) for an expert CYPRES II or for any other CYPRES model? Cabin pressure maintained 3000 feet AGL or above until exit. Exit from 10,000 feet AGL.  Does it impact functionality?

2. CYPRES calculates during initial self integrated test and obtains ground elevation value. If cabin is pressurised after climbing 3000 feet AGL & again maintained 3K or above, does it impact on ground elevation value which CYPRES obtained during self integrated test?

3. How often do you resort to cabin pressurisation for longer duration flights after crossing arming altitude ?

[gowlerk 1,915]

47 minutes ago, randhawa922 said:

3. How often do you resort to cabin pressurisation for longer duration flights after crossing arming altitude ?

I have never heard of this being done. Certainly never in the sport parachuting world. Airtec makes a military model that most likely can be used in this scenario. Here is a link to the manual for the device.

https://dl.cypres.aero/military/userguide/991105_m_cypres_2_users_guide_e_us.pdf

There is some guidance for this on page 36

Edited January 8, 2023 by gowlerk

[pchapman 262]

Seems OK by the manual. Cypres would just get fooled if you started at "ground level" then during the climb the pressure went to below ground level. (Special case: If a DZ offset is set, then the limit is that new level, not zero.)

So climbing to 3000', starting to pressurize and going to a cabin altitude of 3000' minimum (or even dipping down to say 2000'), and then climbing to altitude with the cabin altitude only slowly ascending or level at some value, before eventually depressurizing.... That's little different to a Cypres than climbing in a regular aircraft to 3000', ducking down lower because of some clouds, and then climbing to altitude.

But question #3 makes one wonder what the original poster's skydiving experience is... Since basically nobody uses pressurization unless you are on some very rare, unusual world record with exotic aircraft. It doesn't apply for 99.9999% of skydives.

[SethInMI 145]

1 hour ago, pchapman said:

But question #3 makes one wonder what the original poster's skydiving experience is

I wondered that too, the poster has a short post history but it goes back 6 years, one alludes to being in the military, which makes sense, as military planes are the only ones I know that can pressurize and still have doors that can be used to skydive from. 

Not sure what prompted the question, as you would think ops for military would have standardized a long time ago on procedures, but maybe there are some new ideas for pressurizing on flights that are being debated.

[BIGUN 1,060]

Page 25

991105_m_cypres_2_users_guide_e_us.pdf

[randhawa922 1]

Hey folks thank you so much. I have adequate experience and my question 3 was genuine, the environment I am working right now requires pressurisation at times.

We can definitely pressurise crossing arming altitude of respective CYPRES models. It doesn’t change ground elevation value obtained during intial self integtest.

Thank you and blue skies!!!
 

 

[randhawa922 1]

19 hours ago, pchapman said:

Seems OK by the manual. Cypres would just get fooled if you started at "ground level" then during the climb the pressure went to below ground level. (Special case: If a DZ offset is set, then the limit is that new level, not zero.)

So climbing to 3000', starting to pressurize and going to a cabin altitude of 3000' minimum (or even dipping down to say 2000'), and then climbing to altitude with the cabin altitude only slowly ascending or level at some value, before eventually depressurizing.... That's little different to a Cypres than climbing in a regular aircraft to 3000', ducking down lower because of some clouds, and then climbing to altitude.

But question #3 makes one wonder what the original poster's skydiving experience is... Since basically nobody uses pressurization unless you are on some very rare, unusual world record with exotic aircraft. It doesn't apply for 99.9999% of skydives.

Haha.. It applies to several military ops. Thank you! Blue skies!!

[billvon 2,404]

On 1/7/2023 at 6:43 PM, randhawa922 said:

1. What if the cabin is pressurised after climbing & crossing 3000 feet AGL(considering safe margin) for an expert CYPRES II or for any other CYPRES model? Cabin pressure maintained 3000 feet AGL or above until exit. Exit from 10,000 feet AGL.  Does it impact functionality?

Yes.  A rapid pressurization (or depressurization) will cause the cypres to think that it is climbing or descending faster than is physically possible, and it will throw an error and shut down.  This happened to some cypreses during the WT jumps when the aircraft pressurized.

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2. CYPRES calculates during initial self integrated test and obtains ground elevation value. If cabin is pressurised after climbing 3000 feet AGL & again maintained 3K or above, does it impact on ground elevation value which CYPRES obtained during self integrated test?

Not unless you power cycle it.

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3. How often do you resort to cabin pressurisation for longer duration flights after crossing arming altitude ?

Never.  The one time it happened to me was a screwup.

[randhawa922 1]

12 hours ago, billvon said:

Yes.  A rapid pressurization (or depressurization) will cause the cypres to think that it is climbing or descending faster than is physically possible, and it will throw an error and shut down.  This happened to some cypreses during the WT jumps when the aircraft pressurized.

Not unless you power cycle it.

Never.  The one time it happened to me was a screwup.

Ok, but it can be resorted to for specific requirement and it doesn’t impact functionality of CYPRES