X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 04 Apr 2013 18:25:42 -0400 Message-ID: X-Original-Return-Path: Received: from [64.98.42.215] (HELO smtprelay.b.hostedemail.com) by logan.com (CommuniGate Pro SMTP 6.0.4) with ESMTP id 6181357 for lml@lancaironline.net; Thu, 04 Apr 2013 17:43:03 -0400 Received-SPF: none receiver=logan.com; client-ip=64.98.42.215; envelope-from=bknotts@buckeye-express.com Received: from filter.hostedemail.com (b-bigip1 [10.5.19.254]) by smtprelay04.b.hostedemail.com (Postfix) with SMTP id 9D88F7B849 for ; Thu, 4 Apr 2013 21:42:28 +0000 (UTC) X-Panda: scanned! X-Spam-Summary: 2,-2,0,,d41d8cd98f00b204,bknotts@buckeye-express.com,:,RULES_HIT:72:327:355:379:408:421:472:509:599:800:854:901:960:962:966:967:973:982:983:988:989:1187:1189:1208:1212:1221:1260:1261:1313:1314:1345:1359:1431:1436:1437:1516:1517:1518:1575:1588:1589:1592:1594:1605:1608:1617:1685:1691:1712:1730:1776:1792:1981:2068:2069:2194:2196:2197:2198:2199:2200:2201:2202:2525:2527:2528:2565:2682:2685:2693:2739:2859:2898:2902:2917:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3586:3653:3743:3770:3865:3866:3867:3868:3870:3871:3872:3873:3874:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4048:4250:4321:4379:4385:4605:5007:6117:6248:6300:6657:6658:6678:7652:7688:7754:7875:7901:7903:7904:8583:8599:8603:8828:8957:9009:9010:9025:9121:9163:9388:9868:10004:10026:10049:10360:10394:10848:10919:11027:11232:11233:11253:11257:11656:11854:11914:12043:12049:12050:12198:12295:12438:12517:12519:12555:12740:12776:13091:13139:13146:13230: X-Session-Marker: 626B6E6F747473406275636B6579652D657870726573732E636F6D X-Filterd-Recvd-Size: 36714 Received: from [127.0.0.1] (cblmdm72-240-126-144.buckeyecom.net [72.240.126.144]) (Authenticated sender: bknotts@buckeye-express.com) by omf03.b.hostedemail.com (Postfix) with ESMTPA for ; Thu, 4 Apr 2013 21:42:27 +0000 (UTC) X-Original-Message-ID: <515DF3C2.904@buckeye-express.com> X-Original-Date: Thu, 04 Apr 2013 17:42:26 -0400 From: "F. Barry Knotts" Reply-To: bknotts884@earthlink.net User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130307 Thunderbird/17.0.4 MIME-Version: 1.0 X-Original-To: Lancair Mailing List Subject: Re: [LML] Re: Minimum MP for pressurization References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------010301090609090902090706" X-Antivirus: avast! (VPS 130404-1, 04/04/2013), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. --------------010301090609090902090706 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit I've often wondered about that 31.5" MP figure. It's never been an issue with my aircraft. However, there is one other factor to consider. Some TSIO-550's have been fitted with a non-stock Garrett turbocharger. N4XE has the larger turbos. I talked this over with Allen Barrett (of Barrett Precision Engines of Tulsa, OK.) at the Sedona fly-in. The non-stock version (I don't know the proper designation) was originally developed by Allen Barrett (according to Allen). The only difference is a slightly larger compressor and scroll. The turbine side is identical to the stock turbocharger. The reason for using the slightly larger compressor side is the ability to supply additional volume of air at high altitude, even at lower power settings. (At least that's my understanding.) He indicated that full power was really not available above about 17.5 without the larger compressor due to the lack of air volume. I've have just had the stock turbochargers modified to the larger compressor turbos for about $325 each on another TSIO-550. If anyone is interested, I could supply the name of the company that does the conversion. Barry Knotts TSIO-550, N4XE (And soon, N24XE...) On 4/4/2013 12:50 AM, Robert R Pastusek wrote: > > Dico wrote: > > Hello all, > > I was looking through the TSIO-550 Power Settings Chart and noticed > that it said the min MP for pressurization was 31.5".... I'm just > wondering if this is true for all IVPs? > > I was up to FL170 the other day at 28.5" and the cabin was showing > perhaps 7800. Should I assume that if I was running at 31.5" that the > cabin might only have been showing perhaps 5000'? The reason I ask > is because I'm thinking if we're at FL170 and the cabin is pushing > 8000, then at FL250 (or even FL210) the cabin pressure would be well > over 10,000'. I had thought it might have been because I have a leaky > cabin or something.... but perhaps its because I'm being too cheap > with the fuel.... > > > Dico, > > The Lancair IV-P is designed to operate at a maximum differential > pressure (pressure difference between the cabin interior and outside) > of 5 PSI. Your airplane has a Duke's pressurization/control system > that allows you to set the cabin altitude to a specified value. Most > are calibrated to generate a cabin altitude of 1,000-1,500' above the > set altitude---for a couple of reasons. In any case, the system will > allow pressurized air from the turbochargers to flow through the cabin > until the inside pressure altitude reaches about 1,000' above what's > set on the control. It then starts closing the outflow valve under the > rear seat to maintain this inside pressure altitude. As long as there > is a sufficient supply of pressurized air from the turbos, the > controller will automatically close/modulate as needed to maintain > this altitude-- until the inside/outside difference reaches 5 PSI. The > cabin pressure then starts to decrease (higher cabin altitude) as you > continue to climb. I've attached a chart that shows that with a 5 PSI > differential system, you should be able to maintain an 8,000' cabin > altitude to about 23,000' PA and that the cabin should be about > 10,000' at FL 250. Because of leakage, inefficiencies and calibration > settings , the cabin altitude starts to go up as the airplane climbs > through FL 21-220---for most of us. > > There are two big factors that govern how well this works---supply > pressure/volume and cabin leakage. A high engine power setting > generates a lot of high-pressure air from the turbos. This is > moderated somewhat by the sonic nozzles in the hot side feed (some > airplanes were built with sonic nozzles in both the hot and cold feed > lines; some did not do this), but you can definitely tell a difference > in airflow through the cabin between takeoff and cruise power settings. > > If the cabin is leaky, even max power (38.5" boost pressure) won't > generate enough high pressure air to pressurize the cabin (e.g., you > forgot to activate the door seal). If it's a tight cabin, 25" of MP is > about the minimum that will maintain the 5 PSI difference...and since > there are not anti-back flow valves in this system, pulling the power > below this will cause pressurized cabin air to flow back through the > engine---rather rapidly. > > To answer your specific question, you should be able to maintain a > cabin altitude of about 4500' IF your altitude controller was set > below 3,000' AND your cabin is tight. You can easily check for a > calibration or leakage problem by stabilizing at 17,500' in cruise > with the altitude controller set to 0---or at least below 3,000'--and > check the cabin pressure. Then increase MP by at least 2" of Hg and > again check the cabin pressure. If it increases (cabin altitude > decreases), you can improve the cabin pressure by sealing leaks; if it > doesn't change, you can improve the cabin pressure by adjusting the > pressure controller. > > If you can't maintain cabin pressure at 25-26" of MP, consider working > on the cabin sealing. Requiring 31" of MP to maintain cabin pressure > indicates leaks to me. > > Bob > > > > -- > For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html --------------010301090609090902090706 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit
I've often wondered about that 31.5" MP figure.  It's never been an issue with my aircraft.

However,  there is one other factor to consider.  Some TSIO-550's have been fitted with a non-stock Garrett turbocharger.  N4XE has the larger turbos.  I talked this over with Allen Barrett (of Barrett Precision Engines of Tulsa, OK.) at the Sedona fly-in.  The non-stock version (I don't know the proper designation) was originally developed by Allen Barrett (according to Allen).  The only difference is a slightly larger compressor and scroll.  The turbine side is identical to the stock turbocharger.  The reason for using the slightly larger compressor side is the ability to supply additional volume of air at high altitude, even at lower power settings.  (At least that's my understanding.)  He indicated that full power was really not available above about 17.5 without the larger compressor due to the lack of air volume.

I've have just had the stock turbochargers modified to the larger compressor turbos for about $325 each on another TSIO-550.  If anyone is interested, I could supply the name of the company that does the conversion.

Barry Knotts
TSIO-550, N4XE
(And soon, N24XE...)

 
On 4/4/2013 12:50 AM, Robert R Pastusek wrote:

Dico wrote:

 

Hello all,

I was looking through the TSIO-550 Power Settings Chart and noticed that it said the min MP for pressurization was 31.5"....  I'm just wondering if this is true for all IVPs?

I was up to FL170 the other day at 28.5" and the cabin was showing perhaps 7800.  Should I assume that if I was running at 31.5" that the cabin might only have been showing perhaps 5000'?  The reason  I ask is because I'm thinking if we're at FL170 and the cabin is pushing 8000, then at FL250 (or even FL210) the cabin pressure would be well over 10,000'.  I had thought it might have been because I have a leaky cabin or something.... but perhaps its because I'm being too cheap with the fuel....


Dico,

 

The Lancair IV-P is designed to operate at a maximum differential pressure (pressure difference between the cabin interior and outside) of 5 PSI. Your airplane has a Duke’s pressurization/control system that allows you to set the cabin altitude to a specified value. Most are calibrated to generate a cabin altitude of 1,000-1,500’ above the set altitude—for a couple of reasons. In any case, the system will allow pressurized air from the turbochargers to flow through the cabin until the inside pressure altitude reaches about 1,000’ above what’s set on the control. It then starts closing the outflow valve under the rear seat to maintain this inside pressure altitude. As long as there is a sufficient supply of pressurized air from the turbos, the controller will automatically close/modulate as needed to maintain this altitude-- until the inside/outside difference reaches 5 PSI. The cabin pressure then starts to decrease (higher cabin altitude) as you continue to climb. I’ve attached a chart that shows that with a 5 PSI differential system, you should be able to maintain an 8,000’ cabin altitude to about 23,000’ PA and that the cabin should be about 10,000’ at FL 250. Because of leakage, inefficiencies and calibration settings , the cabin altitude starts to go up as the airplane climbs through FL 21-220---for most of us.

 

There are two big factors that govern how well this works—supply pressure/volume and cabin leakage. A high engine power setting generates a lot of high-pressure air from the turbos. This is moderated somewhat by the sonic nozzles in the hot side feed (some airplanes were built with sonic nozzles in both the hot and cold feed lines; some did not do this), but you can definitely tell a difference in airflow through the cabin between takeoff and cruise power settings.

 

If the cabin is leaky, even max power (38.5” boost pressure) won’t generate enough high pressure air to pressurize the cabin (e.g., you forgot to activate the door seal). If it’s a tight cabin, 25” of MP is about the minimum that will maintain the 5 PSI difference…and since there are not anti-back flow valves in this system, pulling the power below this will cause pressurized cabin air to flow back through the engine—rather rapidly.

 

To answer your specific question, you should be able to maintain a cabin altitude of about 4500’ IF your altitude controller was set below 3,000’ AND your cabin is tight. You can easily check for a calibration or leakage problem by stabilizing at 17,500’ in cruise with the altitude controller set to 0—or at least below 3,000’--and check the cabin pressure. Then increase MP by at least 2” of Hg and again check the cabin pressure. If it increases (cabin altitude decreases), you can improve the cabin pressure by sealing leaks; if it doesn’t change, you can improve the cabin pressure by adjusting the pressure controller.

 

If you can’t maintain cabin pressure at 25-26” of MP, consider working on the cabin sealing. Requiring 31” of MP to maintain cabin pressure indicates leaks to me.

 

Bob



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