---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 08/07/04: 17 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:49 AM - Re: iPod and altitude (Brian Lloyd) 2. 06:18 AM - Re: Alternator/Battery Switches (Robert L. Nuckolls, III) 3. 06:46 AM - Re: Re: 12V VS. 24V Electrical System. (Brian Lloyd) 4. 06:51 AM - Re: 11540 Dudkoff (Robert L. Nuckolls, III) 5. 09:25 AM - Re: iPod and altitude (rd2@evenlink.com) 6. 09:31 AM - 3-position switch (rd2@evenlink.com) 7. 09:49 AM - Re: iPod and altitude (BobsV35B@aol.com) 8. 09:53 AM - Re: 3-position switch (BobsV35B@aol.com) 9. 10:07 AM - Re: iPod and altitude (Brian Lloyd) 10. 10:13 AM - Re: 3-position switch (rd2@evenlink.com) 11. 12:43 PM - XCOM 760 now shipping but... (RV8ter@aol.com) 12. 01:09 PM - Re: iPod and altitude (Larry Bowen) 13. 02:27 PM - Re: 3-position switch (BobsV35B@aol.com) 14. 03:45 PM - KX125 (Mickey Billings) 15. 04:18 PM - Re: KX125 (Franz Fux) 16. 07:33 PM - Re: iPod and altitude (Ernest Christley) 17. 08:05 PM - Re: iPod and altitude (James Foerster) ________________________________ Message 1 _____________________________________ Time: 05:49:13 AM PST US From: Brian Lloyd Subject: Re: AeroElectric-List: iPod and altitude --> AeroElectric-List message posted by: Brian Lloyd On Aug 6, 2004, at 6:19 PM, Richard Tasker wrote: > --> AeroElectric-List message posted by: Richard Tasker > > > 1. All hard drives breathe. If you disassemble one (not a functioning > one please) you will find there is a specific section with air holes > and > a filter. > 2. LCDs are filled with a liquid. Liquids do not expand appreciably > with changes in external air pressure. The LCD will be fine at any > reasonable altitude. > 3. The comment about Gs with a hard drive is right on, but the comment > about "any altitude" is wrong. The other email explanations regarding > the head "flying" on a film of air are correct - as the air density > decreases the lift decreases until you have no margin for any Gs and > you > have a head crash. A single crash may not destroy anything - depending > on how "bad" it is. Or it may just damage the magnetic coating so the > next time it tries to record something there it doesn't work. Or it > could destroy the head and you end up with a several hundred dollar > paperweight! You got all that right. There is one other thing to add: modern disk drives are designed for the heads to "land" on the medium. In olden days the magnetic medium was soft. It consisted of iron oxide in a binder just like magnetic tape. A head touching down on the medium meant damage to the medium. The disk drives therefore would retract the heads completely on power-down. I remember one disk drive I worked on had a set of AA-sized NiCd batteries that would be connected to the voice-coil actuator on power-fail to force the heads to retract. It was crude but effective. Modern drives use a plated metallic medium. It is quite hard and quite smooth. This allows the heads to land and take-off from the surface of the disk many times without damage. It is why we don't worry much about head crashes anymore. Every time you power the disk up or down it experiences a "head-crash." Still, if the head remained in contact with the disk for a long time it would eventually damage the disk. Of perhaps greater consideration is temperature and cooling. In the case of convection (forced air) cooling, as air density decreases you need to move a greater volume of air to achieve the same heat transfer. This is why equipment designed for very high altitude operation is designed for conduction cooling. The iPod is designed to cool by conduction through its case. A laptop is not. A laptop computer at very high altitude may not be able to move enough air to keep its processor and/or disk drive cool enough to operate safely. > I wouldn't take my operating Ipod above 10K feet for any reason unless > I > was a real gambler (I am not). Turned off, it is fine to any > altitude. I think there is probably some leeway with the altitude but given that we don't know how much "headroom" Apple built into the iPod your words are prudent. But I don't think that the unit will fail at 10,001'. I don't even think it will fail at 12,500'. Mine didn't fail at 17,500. And if it did, I don't think it will be permanently damaged if you don't try to keep playing it. And as I said in my earlier message, your results may vary. > Your luck may vary, Seems I lucked out this time, eh? It would be interesting to find out who's drives they use and then find the original manufacturer's data on safe operation. Brian Lloyd 6501 Red Hook Plaza brianl@lloyd.com Suite 201 +1.340.998.9447 St. Thomas, VI 00802 ________________________________ Message 2 _____________________________________ Time: 06:18:41 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Alternator/Battery Switches --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" >Comments/Questions: Hi Bob, I'm hoping to use your OVM-14 on my RV7 >electrical system, based in part on your z11 drawing, but I was hoping to >have two separate switches for the master and alternator field... in your >diagram on wiring the OVM-14 there is a note that says "Battery and >alternator should come on and of together". What is the reson for this? Alternators do not run well without a battery on line. Since the very earliest days of alternator installations, most light aircraft have used interlocked battery and alternator switches to insure that the alternator cannot be left on line without the battery being on also. Notable exceptions are the Bonanza and Barons where Beech went to the trouble of making sure that their alternators performed at minimal standards sans battery. It is my best recommendation that the alternator/battery controls be wired as depicted in the Z-figures and that you maintain your battery such that e-bus loads can be powered for duration of fuel aboard. This approach will offer system performance and reliability unmatched by any certified aircraft I'm aware of. I will invite you to join us on the AeroElectric List to continue this and similar discussions. It's useful to share the information with as many folks as possible. A further benefit can be realized with membership on the list. There are lots of technically capable folks on the list who can offer suggestions too. You can join at . . . http://www.matronics.com/subscribe/ Thanks! Bob . . . -------------------------------------------- ( Knowing about a thing is different than ) ( understanding it. One can know a lot ) ( and still understand nothing. ) ( C.F. Kettering ) -------------------------------------------- ________________________________ Message 3 _____________________________________ Time: 06:46:10 AM PST US From: Brian Lloyd Subject: Re: AeroElectric-List: RE: 12V VS. 24V Electrical System. --> AeroElectric-List message posted by: Brian Lloyd On Aug 6, 2004, at 6:14 PM, Eric M. Jones wrote: > Increasing the DC voltage results in > smaller power conductors since delivered Watts is Amps X Volts and the > size > of the conductor is a function only of Amperes. At higher voltages you can also accept greater voltage drop so you can accept a longer cable run for the same percentage of voltage drop. This becomes really interesting at higher currents. For instance, if I have to have a remote battery for starting, I would much rather have a 28V electrical system because I can tolerate greater voltage drop and still get acceptable performance. Avionics has something interesting now too. Most modern radios use "universal" switching power supplies that will work from something like 10V to 32V. If you have a 28V electrical system the buss voltage will rarely drop below about 15-16V even while cranking the engine. This means that your avionics can be on and remain on without dropping out. This is useful for things that have a significant start-up time like GPS receivers and AHRS. Personally I fall into the 28V camp myself. In doing a new electrical system for my CJ6A I plan to stick with 28V. I will have an equalizer for the two 12V batteries yielding 14V for those devices for which I can only find in 14V flavors. High-power stuff will be 28V Brian Lloyd 6501 Red Hook Plaza brianl@lloyd.com Suite 201 +1.340.998.9447 St. Thomas, VI 00802 ________________________________ Message 4 _____________________________________ Time: 06:51:45 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: 11540 Dudkoff --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" >Comments/Questions: Hello Bob , I am a RV-6 builder with 19 hr flt time. >Van's Alternator failed >ND 18148,ext reg., 35 amp ,no Fan!, with B&G linear regulator.I had a >blast cooling tube. I still cooked the alternator. I understand the most >reliable ALT is the two internal fan type. I am improving the cooling >system by making an external cover on the back of the alternator and force >the air through the internals. Some research I have done suggest that the >internal temperature of the electrical components should not exceed 85 deg >C. Is this correct? Before you charge off and do a lot of work, are you SURE the alternator failed due to lack of cooling? Keep in mind that hundreds of RV's are flying with Van's suggested alternator. All modern alternators are very robust and the vast majority should run trouble free for TBO on the engine. Cooling issues are DESIGNED in . . . if your alternator died of overheat, and it was installed per Van's suggestions, then many, MANY alternators are similarly at-risk for cooking to death. Field experience suggests this is not so. What are your system loads on the alternator in cruising flight? Did you make any changes from Van's recommendations and/or successful installations already flying that might account for an installation issue? The LR-3 has been built in the thousands for over 10 years and experience suggests that this device is similarly suited to operation in airplanes without extra ordinary attention to cooling. Internal temperatures on alternators can exceed 150 degrees C on windings at full load and minimal cooling. Unless you can identify a serious deviation from recommended installation practices, I think it's more likely that your alternator suffered a random event failure of some kind. Are you sure that the Van's alternator doesn't have internal fans? I think ND went to internal fans on all designs years ago. In any case, it should be very easy to acquire a 35-40 amp machine that does have such fans. What size pulley are you running on your alternator. Stock ND alternators tend to come with relatively small pulleys which causes them to run fast on a Lycoming installation. I recommend you stay with the small pulley to keep it cooler and give better output at idle and taxi RPMs. I will invite you to join us on the AeroElectric List to continue this and similar discussions. It's useful to share the information with as many folks as possible. A further benefit can be realized with membership on the list. There are lots of technically capable folks on the list who can offer suggestions too. You can join at . . . http://www.matronics.com/subscribe/ Thanks! Bob . . . -------------------------------------------- ( Knowing about a thing is different than ) ( understanding it. One can know a lot ) ( and still understand nothing. ) ( C.F. Kettering ) -------------------------------------------- ________________________________ Message 5 _____________________________________ Time: 09:25:44 AM PST US From: rd2@evenlink.com Subject: Re: AeroElectric-List: iPod and altitude --> AeroElectric-List message posted by: rd2@evenlink.com Brian >Seems I lucked out this time, eh? Who knows you might be one of the guys who are always lucky. :) Not my case - if the specs say "it'll fail at 10K" mine probably would try desperately failing at 9999 (or earlier). >It would be interesting to find out who's drives they use and then find >the original manufacturer's data on safe operation. Yes, it would. As an extension of this I was wondering: doesn't some military equipment contain hard drives; probably mil specs are are more air density demanding; who makes these drives; also, the cabin is probably pressurized (but drives in mil installations should not rely on that).... More and more food fer thought. In the case of playing mp3 the highest _practical_ bandwith would be about 320 kbs uncomressed (in most cases under 180 kbs or VBR, which falls mostly under 180, produces excellent results, unless it's video-audio). That makes the necessary read speed less than 320 kbs. Hard drives are capable of tens (or hundreds) of MB per second, so the software of mp3 players is designed to awake the drive, read file sections (as much as memory allows) and put the drive to sleep until the next read. A drive works intermittently being awake only a fraction of the playing time. In order to damage it one has to find the moment it's awake and apply g-fources and/or the thin air factor during that time. If it is someone else's drive the laws of statistical probabilities may apply; in my case it's usually Murphy's law/s. Ohh.. well.... Rumen _____________________Original message __________________________ (received from Brian Lloyd; Date: 08:47 AM 8/7/2004 -0400) --> AeroElectric-List message posted by: Brian Lloyd On Aug 6, 2004, at 6:19 PM, Richard Tasker wrote: > --> AeroElectric-List message posted by: Richard Tasker > > > 1. All hard drives breathe. If you disassemble one (not a functioning > one please) you will find there is a specific section with air holes > and > a filter. > 2. LCDs are filled with a liquid. Liquids do not expand appreciably > with changes in external air pressure. The LCD will be fine at any > reasonable altitude. > 3. The comment about Gs with a hard drive is right on, but the comment > about "any altitude" is wrong. The other email explanations regarding > the head "flying" on a film of air are correct - as the air density > decreases the lift decreases until you have no margin for any Gs and > you > have a head crash. A single crash may not destroy anything - depending > on how "bad" it is. Or it may just damage the magnetic coating so the > next time it tries to record something there it doesn't work. Or it > could destroy the head and you end up with a several hundred dollar > paperweight! You got all that right. There is one other thing to add: modern disk drives are designed for the heads to "land" on the medium. In olden days the magnetic medium was soft. It consisted of iron oxide in a binder just like magnetic tape. A head touching down on the medium meant damage to the medium. The disk drives therefore would retract the heads completely on power-down. I remember one disk drive I worked on had a set of AA-sized NiCd batteries that would be connected to the voice-coil actuator on power-fail to force the heads to retract. It was crude but effective. Modern drives use a plated metallic medium. It is quite hard and quite smooth. This allows the heads to land and take-off from the surface of the disk many times without damage. It is why we don't worry much about head crashes anymore. Every time you power the disk up or down it experiences a "head-crash." Still, if the head remained in contact with the disk for a long time it would eventually damage the disk. Of perhaps greater consideration is temperature and cooling. In the case of convection (forced air) cooling, as air density decreases you need to move a greater volume of air to achieve the same heat transfer. This is why equipment designed for very high altitude operation is designed for conduction cooling. The iPod is designed to cool by conduction through its case. A laptop is not. A laptop computer at very high altitude may not be able to move enough air to keep its processor and/or disk drive cool enough to operate safely. > I wouldn't take my operating Ipod above 10K feet for any reason unless > I > was a real gambler (I am not). Turned off, it is fine to any > altitude. I think there is probably some leeway with the altitude but given that we don't know how much "headroom" Apple built into the iPod your words are prudent. But I don't think that the unit will fail at 10,001'. I don't even think it will fail at 12,500'. Mine didn't fail at 17,500. And if it did, I don't think it will be permanently damaged if you don't try to keep playing it. And as I said in my earlier message, your results may vary. > Your luck may vary, Seems I lucked out this time, eh? It would be interesting to find out who's drives they use and then find the original manufacturer's data on safe operation. Brian Lloyd 6501 Red Hook Plaza brianl@lloyd.com Suite 201 +1.340.998.9447 St. Thomas, VI 00802 ________________________________ Message 6 _____________________________________ Time: 09:31:34 AM PST US From: rd2@evenlink.com Subject: AeroElectric-List: 3-position switch --> AeroElectric-List message posted by: rd2@evenlink.com I was wondering if anyone could recommend/direct me to a source for an inexpensive, reliable, certified, small size 3-position switch (all positions "on") to be used to switch an autopilot between 3 signal sources (yaw signals from 2 VORs and a GPS). It could be a toggle or (preferably) rotary switch. Thanks Rumen ________________________________ Message 7 _____________________________________ Time: 09:49:34 AM PST US From: BobsV35B@aol.com Subject: Re: AeroElectric-List: iPod and altitude --> AeroElectric-List message posted by: BobsV35B@aol.com In a message dated 8/7/04 11:26:51 AM Central Daylight Time, rd2@evenlink.com writes: Yes, it would. As an extension of this I was wondering: doesn't some military equipment contain hard drives; probably mil specs are more air density demanding; who makes these drives; also, the cabin is probably pressurized (but drives in mil installations should not rely on that).... More and more food fer thought. Good Morning All, Just a random thought-- Would it be at all practical to place these devices in some sort of pressurized container? A small box with a balloon attached should be able to keep it below a 10,000 pressure altitude fairly easily. If the aircraft has a supercharger, it would be easy to pressurize the box the same way magnetos are often pressurized. How much air exchange would need to take place for cooling, etc.? Happy Skies, Old Bob AKA Bob Siegfried Ancient Aviator Stearman N3977A Brookeridge Airpark LL22 Downers Grove, IL 60516 630 985-8502 ________________________________ Message 8 _____________________________________ Time: 09:53:30 AM PST US From: BobsV35B@aol.com Subject: Re: AeroElectric-List: 3-position switch --> AeroElectric-List message posted by: BobsV35B@aol.com In a message dated 8/7/04 11:32:08 AM Central Daylight Time, rd2@evenlink.com writes: I was wondering if anyone could recommend/direct me to a source for an inexpensive, reliable, certified, small size 3-position switch (all positions "on") to be used to switch an autopilot between 3 signal sources (yaw signals from 2 VORs and a GPS). It could be a toggle or (preferably) rotary switch. Thanks Rumen Good Morning Rumen, Electronics International sells a double pole rotary three position switch to use to switch between shunts for their loadmeter. Probably a lot more than what you need, but it is a robust switch. I don't care for the bulky connectors they use, but I can't see why you couldn't cut the supplied connectors off and use something less obtrusive. Happy Skies, Old Bob AKA Bob Siegfried Ancient Aviator Stearman N3977A Brookeridge Airpark LL22 Downers Grove, IL 60516 630 985-8502 ________________________________ Message 9 _____________________________________ Time: 10:07:10 AM PST US From: Brian Lloyd Subject: Re: AeroElectric-List: iPod and altitude --> AeroElectric-List message posted by: Brian Lloyd On Aug 7, 2004, at 12:48 PM, BobsV35B@aol.com wrote: > Yes, it would. As an extension of this I was wondering: doesn't some > military equipment contain hard drives; probably mil specs are more > air > density demanding; who makes these drives; also, the cabin is > probably > pressurized (but drives in mil installations should not rely on > that).... > More and more food fer thought. > > > Good Morning All, > > Just a random thought-- > > Would it be at all practical to place these devices in some sort of > pressurized container? Should work just fine. > > A small box with a balloon attached should be able to keep it below a > 10,000 > pressure altitude fairly easily. A bicycle tire pump will work too. > If the aircraft has a supercharger, it would be easy to pressurize the > box > the same way magnetos are often pressurized. That seems like hard work. > How much air exchange would need to take place for cooling, etc.? If the box has enough surface area you don't need any airflow. Brian Lloyd 6501 Red Hook Plaza brianl@lloyd.com Suite 201 +1.340.998.9447 St. Thomas, VI 00802 ________________________________ Message 10 ____________________________________ Time: 10:13:40 AM PST US From: rd2@evenlink.com Subject: Re: AeroElectric-List: 3-position switch --> AeroElectric-List message posted by: rd2@evenlink.com Thanks, Bob >Electronics International sells a double pole rotary three position switch >to use to switch between shunts for their loadmeter. Hmmm... will check this out, but I suspect massiveness if it's designed a shunt switch. Something similar to the switches of multimeters (but with only a few positions) might be appropriate. Usually such switches are designed to be reliable. Rumen ________________________________ Message 11 ____________________________________ Time: 12:43:16 PM PST US From: RV8ter@aol.com Subject: AeroElectric-List: XCOM 760 now shipping but... --> AeroElectric-List message posted by: RV8ter@aol.com For those that ordered one already, did they tell you that the "Approvals: FCC, ACA Pending" has actually occurred? I still see that caveat on their web site and in their Installation and Users Manual. Also, does the price of the harness mean the DIY kit or their factory tech built harness to your individual specs which they also discuss? do not archive lucky ________________________________ Message 12 ____________________________________ Time: 01:09:21 PM PST US From: "Larry Bowen" Subject: RE: AeroElectric-List: iPod and altitude --> AeroElectric-List message posted by: "Larry Bowen" XM radio would be easier, IMO - Larry Bowen Larry@BowenAero.com http://BowenAero.com > -----Original Message----- > From: BobsV35B@aol.com [mailto:BobsV35B@aol.com] > Sent: Saturday, August 07, 2004 12:49 PM > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: iPod and altitude > > > --> AeroElectric-List message posted by: BobsV35B@aol.com > > > Good Morning All, > > Just a random thought-- > > Would it be at all practical to place these devices in some sort of > pressurized container? > > A small box with a balloon attached should be able to keep it > below a 10,000 > pressure altitude fairly easily. > > If the aircraft has a supercharger, it would be easy to > pressurize the box > the same way magnetos are often pressurized. > > How much air exchange would need to take place for cooling, etc.? > > Happy Skies, > > Old Bob > AKA > Bob Siegfried ________________________________ Message 13 ____________________________________ Time: 02:27:57 PM PST US From: BobsV35B@aol.com Subject: Re: AeroElectric-List: 3-position switch --> AeroElectric-List message posted by: BobsV35B@aol.com In a message dated 8/7/04 12:14:15 PM Central Daylight Time, rd2@evenlink.com writes: Hmmm... will check this out, but I suspect massiveness if it's designed a shunt switch. Something similar to the switches of multimeters (but with only a few positions) might be appropriate. Usually such switches are designed to be reliable. Rumen Actually, the switch itself is quite small. The shunts are external. It is about one half inch in diameter and maybe one half to three quarters of an inch long. Happy Skies, Old Bob AKA Bob Siegfried Ancient Aviator Stearman N3977A Brookeridge Airpark LL22 Downers Grove, IL 60516 630 985-8502 ________________________________ Message 14 ____________________________________ Time: 03:45:45 PM PST US From: "Mickey Billings" Subject: AeroElectric-List: KX125 --> AeroElectric-List message posted by: "Mickey Billings" I sent this once before but wasn't sure it got there. Does anyone happen to know how the KX 125 interfaces with the Flightcom 403 intercom? I am fairly clear on the 403 but not sure which pins of the KX 125 interfaces with it. I built the isolated ground system shown on the 403 schematic in order to take the CD player out put (which normally goes to speakers) to convert the 8 ohm to 600 ohm for head phone use (pins 1, 18, 19). But not being a educated electronics guy I'm unsure which pins on the King interfaces with pins 1, 17, 21, 8 on the 403! Because I'm not using any other remote heads, I think besides the antennas, and power, this will be the only interface. If anyone has the know how to complete this I would appreciate any help offered. Mickey Billings RV7 N445BH ________________________________ Message 15 ____________________________________ Time: 04:18:09 PM PST US From: "Franz Fux" Subject: RE: AeroElectric-List: KX125 --> AeroElectric-List message posted by: "Franz Fux" Yes we received it before, but I can not help you Franz -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Mickey Billings Subject: AeroElectric-List: KX125 --> AeroElectric-List message posted by: "Mickey Billings" I sent this once before but wasn't sure it got there. Does anyone happen to know how the KX 125 interfaces with the Flightcom 403 intercom? I am fairly clear on the 403 but not sure which pins of the KX 125 interfaces with it. I built the isolated ground system shown on the 403 schematic in order to take the CD player out put (which normally goes to speakers) to convert the 8 ohm to 600 ohm for head phone use (pins 1, 18, 19). But not being a educated electronics guy I'm unsure which pins on the King interfaces with pins 1, 17, 21, 8 on the 403! Because I'm not using any other remote heads, I think besides the antennas, and power, this will be the only interface. If anyone has the know how to complete this I would appreciate any help offered. Mickey Billings RV7 N445BH --- --- ________________________________ Message 16 ____________________________________ Time: 07:33:58 PM PST US From: Ernest Christley Subject: Re: AeroElectric-List: iPod and altitude --> AeroElectric-List message posted by: Ernest Christley bkuc1@tampabay.rr.com wrote: > --> AeroElectric-List message posted by: bkuc1@tampabay.rr.com > > > More food for thought. Hard drives have to be sealed since the heads ride so close to the platter(s). >If there is an air issue with the hard drives that would mean that air has to enter and escape and with no filter, >any microscopic dust particle would crash the heads. A little more food for thought. Completely seal up a hard drive at sea level. Fly to 17500' and watch it deform and pop. My son's computer had a Seagate drive die just a few days ago and I took it apart to show him how it works. The top was an aluminum shell held on by a strip of aluminum tape. In the center left of what would be the top was a 1/8th inch hole that was covered on the outside by a plastic cover. I'm sure there was a filter under the black cover, and there is also a filter inside the disk that would capture any dust particle as it spun around inside the case. Pull a few HD apart. In each one you'll find some way for the air pressure to equalize. I don't think it is just that Brian got lucky. This is a complete guess, but I would think that the iPod would arrange the HD such that the platters spun vertically. The R/W heads would not be floating above the discs, but beside them. It doesn't have gravity contributing to a head crash in that case. My other guess is that head crashes can't happen with a tail wind. -- http://www.ernest.isa-geek.org/ "Ignorance is mankinds normal state, alleviated by information and experience." Veeduber ________________________________ Message 17 ____________________________________ Time: 08:05:57 PM PST US From: "James Foerster" Subject: AeroElectric-List: RE: iPod and altitude --> AeroElectric-List message posted by: "James Foerster" Music lovers: Rather than pressurize the iPod, getting a solid state MP3 player makes more sense. I saw that 1 GB of compact flash memory was $169 at Best Buy recently, and prices will only drop. Of course, if you fly below 10,000 feet most of the time, this is not a consideration. Jim Foerster, J400, 80% done