Heater and fuel gauge gremlins

On my last flight back from taking the kids on a trip Disneyland I came back IFR, went through the clouds and popped out on top around 9k.  Over the Tehachapi's there were reports of turbulence and I wanted to stay out of the clouds as they pushed higher over the mountains.  ATC let me go to 13k even though I was heading west which was nice (west should be 12k or 14k) since I didn't have o2 with me.  The problem was at 13k and a cold front hovering over California, it was far far below freezing temps up there and my heater wasn't keeping up.  It's putting out warm air but not toasty warm like it should, and my wife and young son were cold in the back.  After some asking around on Beechtalk.com (amazing resource) about my Janitrol heater system, some things to check for:

• Fuel pressure, should be at least 7 psi
• Fuel injector nozzle - clean if that doesn't work, overhaul/replace
• Spark plug - cleaning a plug with a rag and maybe a mild 3M pad is fine. If the plug was sandblasted its basically trash. That glazing on the ceramic is vital for proper ignition. And just as important as a clean (New) plug is on a Janitrol, a properly set gap is just as important. Verify its .156-.188
• Check heater ducting for collapses and breaks

I took the plane into the shop and they cleaned the nozzle and the plug and we put them back in.  Fuel pressure was reading 9psi but on my test flight it still wasn't putting out great heat.  We ordered a new nozzle and plug so hopefully that will do the trick.  I also seem to be hearing more wind noise than normal so I wouldn't be surprised if there is a break in my vents somewhere though.  

Also my left fuel gauge sometimes drops off to zero. The fuel gauges have a circuit board on the back of the instrument panel just above the gauges.  The board reads the signal from the fuel sender and amplifies it for the gauge.  It sounds like I might have bad connection or a bad circuit board.  Beech wants $1500 for a new one which is clearly insane the parts couldn't possibly cost more than $15...  these guys have an after market but it will still be around $500 unless I can find another option... sigh...

http://www.birksaviation.com/

PilotsNPaws Mission

I joined PilotsNPaws some time ago but with my hectic schedule I just hadn't been able to make a rescue mission work yet.  Today with the help of an awesome PilotsNPaws advocate Sue Clark I was able help rescue two great dogs.  The mission was straightforward...  a Lhaso Apso and a pit mix were about to be put down in Bakersfield.  They needed to get out to another shelter/rescue center where they might have a chance to find adoptive families.  I was headed south anyway to fetch some family for Thanksgiving, so why not make a little detour?

I greeted Sue at KCCR this morning.  I had never met her before but came to find out she was a highly experienced, retired professional pilot with 20,000+ hours and lots of interesting stories to share.  She volunteered to accompany me on my first mission to show me the ropes and help me handle the dogs, provide crates, and maybe a few piloting pointers.

We were expecting some weather but it turned out to be a beautiful day, albeit windy and blustery.

Typically when you see that kind of haze on the ground in California it means smooth still air, but this time it was actually dust kicked up by strong surface winds.  We fought against 40 kt head winds on the flight south, and moderate turbulence in the mountains over GMN.  I picked up my passenger and then we made our detour to KBFL where we picked up our other "passengers".

I have mixed feelings about pit bulls.  This one was a mix but clearly a lot of pit in her.  I don't blame the dogs, but unfortunately when you mix a lot of breed specific behaviors with all the idiots out there who abuse, neglect and generally miss care for this type of dog, bad things result.  I have no doubt that breed tendencies cause these dogs to act unpredictably, often in terrible ways.  The fighting breeds are dangerous, clearly.  Therefore it was with some trepidation that I agreed to help rescue this one, on assurances that it was sweet and totally 100% socially adjusted to both humans and other dogs.  When I met "Stacy" I  was relieved to realize that was indeed the case.  This was a very sweet dog. She just wanted to be pet and had no aggressive tendencies whatsoever.

The Lhaso Apso was just a total love.  A lap dog basically who just wanted to be held.  He was very timid and was shaking with fear when I took him out of the plane.  This one... "lucky"...  will make someone an excellent companion.

The counter benefit of the winds was on the way back we saw 214 kt ground speeds at 6500 ft, staying low for the dog's ears sake.  Mission accomplished!

Professional Instrument Courses PIC (iflyifr.com)

With the winter weather here and being that it's been 11 years since I got my instrument rating, I figured it would be good time to do a comprehensive IFR refresher. I do an annual IPC for insurance and proficiency reasons, but I live in California... nearly all of these have entailed flying around for 1.5 hrs in CAVU conditions. The last real actual I got was last May unless you count blasting through the summer marine layer at Colemill Baron climb speeds over 2000 fpm which means 1-2 minutes in the clouds at most.

So I just blocked off three days from work and hired PIC to come to me for some IFR adventure time. The plan is to take a little trip and go hunt down a lot of actual instrument conditions. Low approaches, clouds, rain etc. Typically these guys come to you and you put them up in a local hotel for their stay and they prep you for the IFR rating at your local airport. Instead we will go up the western coast towards Seattle and we'll be bound to find some bad weather. I'm already instrument rated so that pressure will be off... just about practicing some stuff I don't often encounter with the family in tote and adventure! Should be fun... departing Dec 22nd!

Soon, another Don Copeland masterpiece...

Don Copeland pinged me with a last minute slot he has open for the paint starting next week... unfortunately I have a trip planned for Thanksgiving so that's not going to work for me, so he is going to put someone else in front and slot me in after that which means I'm finally getting close.  Paint is really the final mile in the total restoration of this wonderful airplane and it's going to look amazing.  I also finally decided on the stripe color, it's going to be...  :)

IPC in the books

This weekend I completed my insurance mandated anual IPC.  Typically I do it with BPPP or BPT training program but this year BPT at Concord conflicted with a trip I had down to Palm Springs.  We had a great flight down to Palm Speings and for the first time in my jaunts there, no turbulence through Banning pass.  We also stopped to pickup grandma on the way, nice to have a plane that can easily fit five!

Anyway from now on October is the month to go to Palm Springs.  I landed at Bermuda Dunes this time which is closer to where I normally stay at Rancho Las Palmas.  Bermuda Dunes was a convenient spot with easy rental car access so I think it will be my new preferred spot vs Thermal from now on.

So the Palm Springs trip caused me to miss this years BPT but one of there instructors was in town for it so I contacted Jim Gruneisen for an IPC.  I managed to squeak one out but it was tough!  It's one thing to fart down the ILS with the GPS and the autopilot working but quite another with an engine out and the AHRS and ADC inop!

Annual good news

The annual is completed and no news is good news.  They also completed the 500 hour spar web inspection and no cracks were found, which is great.  The spar doubler kit costs something like 5k or more to install and that would be a nightmare.  The reason it took an extra week was the fuel injector lines were showing some signs of chaffing so they ordered some new lightweight clamps to better secure them.  Should be able to pickup the plane tonight or tomorrow just in time for a trip to Palm Springs and I'm all legal for another year.

Annual time

This week I took my plane in for annual and got the inspection report back this morning.  I wasn't expecting anything major since at this point my plane is like new, however there is always something.  It came back just rosy, although they have yet to complete the spar web inspection so I'm fingers crossed on that one.  Here is the report:

Compressions X/80

Left: 68 64 62 70 72 70
Right: 62 72 64 64 72 70

Mag Timing: Seems to have slipped a bit, adjust back down to 20deg

Change oil/filter
Service spark plugs
Small injector line bracket needs to be replaced

Some chaffing, install a few clamps on fuel lines

Fuel injector nozzles - clean fuel nozzles
Check and clean fuel metering valve screens

Left cowl flap actuator chaffing breathing tube need to secure it

Left main landing gear strut - service struts


That's basically it.  There is also a small hole in one of the airboxes.  The 35 year old aluminum just doesn't hold up forever however mine are still in decent shape.  Cygnet makes a replacement unit but I'm not sure about pricing, they do look gorgeous though!

For now I think I'll keep what I've got.

Tailwheel refresher

I decided to commemorate 9/11 today by going out and doing a little fun flying. I hadn't flown a taildragger in 10 years. I rented this 7ECA from Attitude Aviation at Livermore.  They also have a basic acro course I think I will do.  These things are a ton of fun and the seat of the pants feeling is really so different from the Baron.  It's not about instruments or speed in these things, it's just about being low and slow and you can make it do some crazy things like hold full rudder deflection and opposite aileron and basically do a big aerial skid out.  Here is a short video of my flight, I'm glad the camera SD card ran out of space so no one could see how ugly my landings were. What a hoot, I really need to get one of these suckers. 

Can't handle

Here is a my new $700 door handle from Avstat Aviation down in Van Nuys...

Ridiculous, clearly... but the pin sheared off in my old handle 3 times in the last year or so.  I finally learned how to drive a new pin, but something was clearly wrong with the handle and it seemed like a safety issue that I could be stuck inside.  The last time it sheared off as I was getting ready to head to LA to pickup grandma. It came off causing me a few hours delay, which caused me to be late to the pickup, which caused me to be late getting back, which caused my wife to delay picking up my youngest son from summer camp, which caused him to try out the obstacle course, which caused him to break his arm.  Clearly I can't stand for this, and decided to break the accident chain with a new door handle.  The cool thing is, it has a green "Closed" indicator and a "Red" open indicator.  It is solid and my door seal is now perfect.  There must have been something missing or worn in the old handle.

New glass

I'm almost embarrassed to report what this cost me, but suffice it to say it was a lot but I'm pretty stoked on the result.  The front windshield alone was $3250... and that little piece of anodized aluminum in front of it that holds it in place was $1500.  Where else but aviation can you replace your windows for the price of a car?

Oh well...  it looks awesome.  Jim finished up today, here is the new profile with the tint.

That should keep things cooler and less glaring when the big 10,000 ft sun is slamming the plane.  It really creates a nice internal cabin feel too.   Here is the money shot...

Perfect new front... apparently Jim had a heck of a time getting it in due to my custom one piece panel (I got rid of the floating panel with the last avionics upgrade).  The cutouts were modified by EAM when they did the panel install which made his life somewhat difficult, but he got it in and now it's ensconced in nice aluminum frame vs before which was basically a big glue job.  Jim finished up around 6 pm and cleaned up the panel, the glare shield and headliner and got everything back together before heading out in his dually fifth wheel mobile home setup for his next stop which I think was down in Fresno... he thinks it's hot here, just wait until Fresno :)  The glue needs to set and I'll be in the air to test everything out by Wed.  All ready for the ultimate paint job and I'll be only 3 minor imperfections away from the ultimate perfect and immaculately restored Baron... I won't say what they are yet...

window masterwork!

Jim from DBMods is truly an artist.  The work is perfectly done, rivets set beautifully.  I feel bad for the poor guy as we're having quite a heat wave and it's been 100 degrees plus in my hangar.  I have fans, but no AC.  Nevertheless, the work is awesome!

Jim, the mobile window guy

The windows on my plane are in pretty good shape, but with the summer heat and no AC in my airplane, I have been wanting to tint the back windows to keep things cool and also keep the sun from beating down on my kids in the back.  There are a number of low budget solutions to tint windows, here is one from Mike Caban (http://csobeech.com/windowtint.html)  But I wanted a professional installation and nothing about my plane thus far is low budget, why start now?  So I was seriously considering these specialized inserts from G&D aero.  (http://www.gdaero.com/products/beachcraft)

I also wanted to add a vent on the copilot side and since that was my cloudiest window, I figured I might as well replace it.  When I bought my airplane, Paul McCracken advised me, "if you ever do your windows, make sure you go to Jim the mobile window guy".  Hmmm, Jim the mobile window guy?  Okay, I put that one in the back of my mind.  Then when speaking with Don Copeland about my paint job he said, "If you want to do your windows make sure you do that before you come to me for paint... Jim the mobile window guy is in California right now I think".   I asked my friend Jerry Alves and he said "Oh yeah, Jim the mobile window guy is an artist".

With those words I decide to contact "Jim the mobile window guy" who turns out to be the owner of DBMods (http://dbmods.com/)  I contacted Jim, and it turns out he is extremely busy and a real character.  He has been rolling around the country in a big Dodge dually truck with a 60 ft fifth wheel on the back replacing airplane windows for the last 30 years.  I was lucky to get on his schedule, and somehow the timing all worked out and yesterday he rolled into my airport wearing a Hawaiian shirt and flip flops, with a cigar hanging out of his mouth and carrying my new windows.

Notice that's two windows... as tends to happen to me with this plane, I seem to have found myself in another "while we're in there" project.  I want a vent on the copilot side, and that window is a bit cloudy so I decided to replace it.  Solar Gray will undoubtedly look the best with my new paint job, so if I'm going to replace that window I really should replace the other side as well.  Oh, and there is a small scratch on the front one and that one should be Solar Gray too.  Oh, and about the G&D inserts?  It turns out they cost as much as new tinted back windows and they add 30 pounds of weight.  Who wants to pay more and give up 30 pounds of useful load?  Not me... so at the end of the day, Jim is replacing all my windows!

The back ones are 50% tint 1/4" and the front is 3/8".   I also bit the bullet and am having him install a new $1500 frame for the front so he doesn't have to drill into the windshield fiberglass which can sometimes cause cracking.  So a week or so of downtime while Jim the mobile window guy works his magic on my plane!

Begone ADF!

I haven't flown an NDB approach since my instrument training, and even then I didn't do it well.  They're easy in no wind, basically you just put the nose on the same heading as the needle.  In any kind of cross wind though, I was always confounded at maintaining a given radial and ended up flying a homing pigeon approach.  I hated the fact that the rental plane I was training in at the time was equipped with one and that therefore my instructor thought it was super important that I mastered it.  I can't say how many hours I wasted trying to learn to fly them well.  All of that was wasted effort too, as I wasn't tested on them on my checkride, and of course since the approaches are basically obsolete and have been for some time, whatever skill I had mustered was promptly lost after I got my ticket.  I haven't looked back since, my plane has not had an ADF (the instrument used to fly the NDB approach) since I bought it.  Good riddance... except for this:

That metal thing hanging down is the battery drain, which is over a foot long so that it can also serve double duty as the attach point for the long wire which connects the NDB antennae to the tail.  It always bothered me that this huge honking stick of metal is hanging out in the breeze creating drag.  Some people cut them down with a hacksaw, but I couldn't do that to my plane.  Then I found this:

It's an STC'd replacement part from a company called South Seas Ventures (http://www.southseasparts.com).  That little hunk of metal which probably cost $4 of course costs $90 with the FAA paperwork attached, but I bit the bullet. 

Much better!  That ought to be good for what, 1 kt or so?  Maybe...

Which stripe?

My deposit is in to Don Copeland for paint.  I'm probably looking at October at the earliest to get my slot into his packed schedule, but I've been experimenting with Photoshop and testing out various schemes.  I'm pretty much settled on the base colors and overall scheme, but I can't decide on the color for the stripes... hmmm..

Red?

Yellow?

Or Blue?

Tough decision!

Redbird Baron

My friend and CFI Mark called me up and said that the FBO at KCCR (Sterling Aviation) had just bought a full motion Baron simulator.  Ironically the line guy had just told me about it while I was fueling up that very morning and I had made a mental note to go check it out.  It turns out Mark will be doing some training in it, and being a high integrity instructor he figured he'd better learn the mechanics of it before charging his students.  So would I be his guinea pig?  Hell yes!

Here is the cockpit, setup as a G58.  I haven't flown a G1000 in awhile, and not since I installed the GTN's in my plane.  The logic is mostly the same but without the touch interface it's nowhere near as easy to use.  The G1000 is a great system, but to be frank I don't consider it an upgrade over a G500 + GTN 750.  The G2000 on the other hand is in another league.  But I digress, the RedBird does a pretty decent job of simulating the Baron.

There are few missing details such as there are no mag switches, you just just turn the keys to fire up both engines.  Like nearly every simulator I've flown, the sensitivity is a little over done and the throttle and prop controls are way too smooth and precise.  Also I noticed it does a strange turbulence type of simulation whenever you pull the props back.  I think it's trying to simulate a slowdown but that's not how it feels in the real world when you retard the props.  All that said, this simulator is actually really really cool.  The wrap around screens really give you a sense of being in the cockpit, and the motion simulation is quite realistic.

There are a few other niggling things that are either small issues or just things we just couldn't figure out.  Mark drained the fuel from one of my tanks via the instructor station, and the fuel annunciator came on and the fuel gauge went to zero, but the engine kept right on humming.  I didn't see a crossfeed switch and I certainly didn't enable it, at least not intentionally so maybe chock that up to a bug or a shortcoming.  Then he failed the engine completely and it had a nice yaw, but not quite the real thing.  I caged it and it feathered nicely, but then he gave me the engine back and it stayed feathered after I put it all back.  No accumulators?  Okay, I had to restart it with the key.  Overall though these pesky details are pretty trivial... the simulator is extremely cool and realistic, and the motion sensations are very good.  To learn the basics or even to practice procedures and simulated emergencies, the RedBird sim is a winner.

Beautiful misery

This weekend we hopped in the Baron and flew to Sedona.  Despite my best intentions, we got a late start on Friday.  I had to finish up some work in the morning, and by the time we got to the airport and were all loaded up it was mid day and the winds were already picking up.  Arizona was calling for scattered thunderstorms,  but no big deal... my plan was to go VFR, fly to Palmdale and hang a big left and then scoot across the Mohave desert straight to KSEZ with an agenda to see and avoid any build ups.  Besides, I have onboard XM for nexrad and onboard radar... what could go wrong?

Problem was, the flight started out with light chop and by the time we passed Bakersfield we were well into the afternoon thermals.  I'm not a big fan of turbulence, but flying alone or with another pilot would have been fine, but with the family in tote it was no fun... no fun at all.  We slogged through another hour and a half of continuous moderate chop and occasional 500-1000 fpm up and down drafts.  There was a scattered to broken layer at 11,000 which went on up to 30,000 in places where the CB and TS were towering so there was no getting on top.  My boys were miserable and accusatory glances and tone of voice from my wife were piercing.  Finally I decided to stop and take a break so we landed at A09 which is a shit hole airport in Bullhead City Nevada, with no toilet and not much else except a narrow strip, and both boys stumbled out of the plane and curled up in the fetal position on the concrete.  Terrible.

But we're only 45 minutes away at this point, and muscle on we must!  We gave the boys some turkey jerky and some coconut water and revived them slightly, hopped back in after finding a bush to pee on and soldiered on... a thousand feet into the climb the bumps hit again and we were getting tossed around on the laborious climb to 7500 ft, dodging the buildups and struggling to keep the nose pointed towards Sedona... when my younger son utters those famous last words... "MY TUMMY HURTS!!"   and then 30 seconds later pops like a water balloon and spews vomit everywhere.  Then my older boy in the back yells "IT SMELLS BAD" followed by my wife saying "Oh my god, oh my god" while my six year old proceeds to projectile vomit and she struggles to catch it... meanwhile we're getting pelted with hail as the nearby TS starts throwing rain and hail our the top and tossing it 30 miles away.  misery!  Worst flight ever...  until the red cliffs of Sedona finally appeared and we all marveled at their beauty... sorry but my poor photography skills don't even come close to doing it justice...

We landed, the boys tumbled out and we proceeded to clean up the barf.  Within 20 minutes, all was forgotten as we absorbed the beauty of the place, and then the TS's closed in and it started raining.  What a beautiful airport, and what a stunning town.  I've been there before but I forgot just how beautiful those red bluffs are and what a cool little town Sedona is. Despite the rough start we met some friends and an amazing weekend.

My wife resolved to return on a commercial flight, but I finally sold her on a zero dark thirty departure. We got as close as we could and ended up getting out wheels up by 7:30, which is pretty darn good for us late night folks... and had a smooth ride as we hauled ass across the desert with the tired pax sleeping soundly....

All in all an awesome weekend, but I'm resigned now to no family flights across the desert unless it's early morning or night, or else I'm in something pressurized and capable of cruising at FL 230.  Hmmm... those TBM's do look nice...

Missed the missed

I flew down to Camarillo to have lunch with some friends and visit my company's team in Westlake.  I went VFR.  I knew it was overcast at KCMA but figured it was just the marine layer and would burn off by the time I got there. It became clear it wasn't going to burn off (XM) and so I requested a popup IFR. In fact the weather deteriorated and the field went IFR. LA center kept telling me to ask the next sector controller for IFR and it wasn't until I got to Mugu approach and was 10 miles from the airport that they finally acknowledged my request, but there were 5 or 6 planes ahead of me so he told me to maintain VFR and started to vector me on a long final. Since I was VFR I had to stay out of the clouds obviously, and that meant staying at 7500 ft since the clouds were up to 5000 ft. 

I got the ATIS again and they were calling for 2300 overcast, 1300 broken. I finally got vectored onto the GPS-Z 26 approach course but I was still super high and well above the glideslope. I went into the clouds and then heard the girl ahead of me go missed. hmmm... with such high ceilings people going missed is usually an indication that the field reports are optimistic at best.  Generally I don't like to descend at more than 1000 fpm while in IMC, so I stuck to that rule and came down slower than I needed to in order to intercept the glideslope. I realized I'd be high but the tower repeated ceiling 1300 broken. I figured I'd pop out and have plenty of time to descend more rapidly in VMC. Instead I was still in the clouds at 700 ft. Just as I was about to go missed I popped out and there was the runway but I still felt I was too high to safely land on the remaining runway, the tower ask if I was going missed and I replied "request special VFR circle to land 26". He told me squawk VFR make left traffic and so I did and came screaming overhead the cafe at 500 ft.  :)  Got a good ribbing from the guys on that one.  

Crappy weather!  Pretty unusual for Los Angeles to be cold and overcast when Northern California is 20 degrees warmer, sunny and gorgeous.   

Bose A20 Pirep

For headsets I've got two Zulu 1's and one Bose X as well as a QT Halo and then a mish mash of non-ANR sets.  I've had LightSpeed Zulu's for a long time and they are a good headset, and until now were what I prefered to wear.  The Bose X is pretty good, but I have big ears and the cups wouldn't quite fit over them.  The QT Halo is okay in a pinch and the price is right, but I just don't like the in-the-ear headsets and it's nowhere near as good at drowning out the low pitch noise.  So when I had a full ship, the kids would take the Zulu's and my wife would wear the BoseX, and I'd wear the QT Halo.  I finally decided I can't handle the in the ear thing anymore and I'd get a new set, and so I bought the new Bose the A20.

This is the hands down the best and most quiet headset I've ever worn, and it fits over my ears.  Hurray!

Highly recommended.  It's so ridiculously quiet you almost can't hear the engines.  It drowns out nearly all the low frequency vibrations and so you just hear a light higher pitch rumble and feel the smooth vibrations of the big bore Continentals.  The sound coming from the XM sounds amazing too, it's like a concert hall.  I'm going to sell all my other headsets and get 3 more of these suckers.  They're pricey but worth it.

Buzz Kill

In all my free time, haha, I help run a local flying club.  I finally convinced the other club managers that we should update the airplanes with modern WAAS gps units, so we did.  I coordinated the install with Executive Autopilots up at KSAC.  Overall a great experience and a solid shop I highly recommend for local avionics work.  Here is how the installs turned out:

Our venerable 172 gets a GTN 650

Our 182RG gets a GTN 750

Sweet, now I'll have good solid IFR backup for when my plane goes to the paint shop... I sent my slot reservation deposit off to Don Copeland, but he's super busy so it's unlikely he'll be able to get to it until Octoberish.  Must have patience for the master!

While I was up at Executive Autopilots I asked Dan the owner about a problem with my XM that's been bugging me for some time.  I hear an constant background buzz when the music goes soft.  He said I probably needed to install a noise isolator between the audio panel and the GDL69A.  It was only a $30 part so I decided to go for it.

It gets installed in the radome

Just that little black box right there smack in the middle of the photo above the wire bundle.

I still hear it ever so slightly, but it's definitely improved.  No one would notice unless they had good hearing and you asked them to listen for it in the lull between songs.

Momentary ice not so momentary

On today's flight I started picking up light to moderate rime ice pretty quickly, I hit momentary on the windshield ice to get her a squirt to get it clear, but when I released the switch it kept streaming out. Doh, no matter where I put the switch it wouldn't stop and I used up all my fluid in a matter of a few minutes. Luckily I climbed 2k feet and got on top and eventually it sublimated away, but obviously something I need to get fixed! 

Oh well, another squawk to deal with!  

My flying club finally decided to do some avionics work on our Cessna's so I flew our 172 up to Sac to get that done.  It had been some time since I've flown a 172, so despite my 95 kt landing speed and endless float, not to mention the sunrise launch, I had some fun with it...

While I was there I talked to the shop about updating the GTN's in my Baron.  When we went to pickup the plane, I went ahead and had them do the software update.  The difference is amazing, it's like the units have been updated with a faster processor, everything is more snappy.  The frequency buttons change quicker, and the backfill render is at least 2x faster.  More importantly, I now get geo referenced charts, woot!

Cool, just in time for a trip.  Here is one of my copilots

Some beautiful weather lately, at least from the air