United 777 w/MEL'd APU Makes Headlines

[Guitar rocker]

UAL should have known better than to do that.

 

[MJG]

I curious to know why airliners/RJs are engineered that way. The plane I fly, albeit much smaller, is capable of having a GPU engergize the air conditioner; the vapor cooling cycle system as it is called, runs on electricity as do the blowers. Do the airliners lack a/c because the volume of air in the cabin would require too many units or too big a cooling unit to make it practical? Certainly, this is not the problem with the RJs. Is it a weight saving measure? Thanks in advance.

FoF

Basically I guess it boils down to size. The shear volume of an airline sized aircraft's cabin, even a "regional jet", it just too large for any kind of electrical air conditioning unit to be effective without paying a high price in either weight or electrical consumption. Therefore high volumes of pneumatic air are required for heating and cooling the cabin. Those can only be produced by the engines or the APU. The engines or APU can send bleed air to the pneumatic air cycle machines (PACs) which are capable of cooling/heating high volumes of air which is then pumped into the cabin for pressurization and air conditioning.

 

[91100 100 set]

When I was at Continental Express we averaged one death a year in IAH from heat related issues in the cabin.

You serious Clark, one a year?

 

[yournextFO]

Largely weight and maintenance...the original 707's and DC8's used to have vapor (freon) cooling units, but they were heavy, maintenance intensive and used a lot of electricity...

 

[jman90]

Weight is the main issue. Think about lifting a window-mounted room air conditioner. If the cabin volume is small the plane may have a vapor cycle air conditioner. Larger cabin planes are air conditioned by the aircraft's air cycle machines which also pressurize the cabin. They are also called PACs for Pressurization and Air Conditioning. They need air from an engine/apu/or huffer cart (which seem hard to find when needed)

 

[FlyPig]

A/c

Most transport category and regional aircraft have the ability to run the packs off a huffer cart. For fuel savings your companies are probably urging the use of jetbridge power when cooling isn't required. With the APU deferred in hot weather you may think the only option is the AC cart, but ask your mechanics how to run the packs off the huffer and by using jetbridge power or the GPU. It's not in your QRH or CFM but the good wrenches know how.

Another thing is the perennial windshield overheat problems. Your checklist may say to turn it on before engine start, but you really only need it before takeoff. Save yourself a return to the gate by not putting heat to your already hot windshield until you need it.

I second the guy who mentioned the mishap regarding closing the throttles at 50 feet while already too slow. It's called judgement and it trumps procedure any day.

 

[Dangerkitty]

You serious Clark, one a year?

Yes Cousin Eddie I am serious.

 

[CrimsonEclipse]

A while back, FLL terminal 3 (now terminal 4) had a fire alarm and
evacuation onto the ramp. The terminal was full of elderly and they
were dropping like flys on the 95F 95% humidity ramp. I think we
lost 7 of them that day.

Not knowing what resources were available, I can't judge the
capt.

CE

 

[time builder]

I work the ramp in LAS which gets a little hotter than back east. It was 105 today and it seemed cool.

Yes, but it's a "dry heat." LOL. I can't count how many times I've briefed my PAX this summer that we just need to get in the air quickly and it'll cool off 20 degrees. VIVA LAS VEGAS.