Questions if you are bored

[safepilot24]

Some more questions from a thankful but starving CFI:

1.) Suppose you are flying a 2000 C-172 Skyhawk that has a red beacon on the vertical tail, and a white strobe light on each wingtip, and the beacon is inop...can you still fly day VFR as per 91.205? Reg states that for small civil aircraft, certificated after 1996, that's me, aircraft must have operable, "approved aviation red or aviation white anticollision light system."

Do my white strobes count as an "approved aviation white anticollision light system?"

What about 1979 C-172's that have red flashing beacons but no strobes. I want to be legal, but display some common sense towards collision avoidance as well.

2.) Which is worse and why....Skidding spins or slipping spins? (Seems to be the hottest question on the CFI checkride right now)

3.) For C-172 Skyhawk, the PIM specifies to "increase distances 10% for each 10 degrees above standard temperature." Can I take this to be a linear relationship between performance values and temperature? (i.e, if temperature is 7 degrees above standard, increase distances 7%?)

4.) Calibrated airspeed question: CAS is IAS corrected for instrument and position errors. If you look in the C-172 PIM, there is an airspeed calibration chart that shows the following:

KIAS 40 50 60 70 80 90 100 110 120
KCAS 49 55 62 70 80 89 99 108 118

The way I interpret this is at high angle of attacks, the pitot tube is not collecting the same total pressure since it is meeting the relative wind at an angle. Calibrated and indicated are the same at 70-80 since these are critical approach speeds, and calibrated is actually slightly less at high speeds because the faster moving air across the static port experiences a significant pressure drop which makes it seem like less static pressure, thereby making the pressure difference appear to be greater. Am I correct in my assumptions? I just want to make sure I understand the "instrument and position" errors the definition is referring to. Any other position or instrument errors I should know about other than slips?

5.) Most light GA aircraft are equipped with 2-12 volt batteries connected in series. Are these considered 35 amp-hours, meaning will they run 35 amps for one hour or 70 amps for half of an hour? I am trying to gain a better understanding of how much I can run off the bat in case of alternator failure?


Thanks everyone.

 

[safepilot24]

These are good questions...I can't believe no one has a response?

 

[Singlecoil]

Some more questions from a thankful but starving CFI:

1.)Do my white strobes count as an "approved aviation white anticollision light system?"

Yes.

What about 1979 C-172's that have red flashing beacons but no strobes. I want to be legal, but display some common sense towards collision avoidance as well.

They count too. If you have the red tail beacon and the strobes, then consider it redundancy.

2.) Which is worse and why....Skidding spins or slipping spins? (Seems to be the hottest question on the CFI checkride right now)

I don't know. Do you mean entering the spin from a slip or a skid?

3.) For C-172 Skyhawk, the PIM specifies to "increase distances 10% for each 10 degrees above standard temperature." Can I take this to be a linear relationship between performance values and temperature? (i.e, if temperature is 7 degrees above standard, increase distances 7%?)

Yes, it is linear, you can interpolate.

4.) Calibrated airspeed question: CAS is IAS corrected for instrument and position errors. If you look in the C-172 PIM, there is an airspeed calibration chart that shows the following:

KIAS 40 50 60 70 80 90 100 110 120
KCAS 49 55 62 70 80 89 99 108 118

The way I interpret this is at high angle of attacks, the pitot tube is not collecting the same total pressure since it is meeting the relative wind at an angle. Calibrated and indicated are the same at 70-80 since these are critical approach speeds, and calibrated is actually slightly less at high speeds because the faster moving air across the static port experiences a significant pressure drop which makes it seem like less static pressure, thereby making the pressure difference appear to be greater. Am I correct in my assumptions? I just want to make sure I understand the "instrument and position" errors the definition is referring to. Any other position or instrument errors I should know about other than slips?

You are correct, due to the installation of the pitot tube, it won't be accurate at all angles of attack. Generally they rig it to be the most accurate at approach speeds, as they are the most critical. I've never heard your idea about a "significant" pressure drop from air moving over the static ports, but you might be right. I wouldn't classify a 2 knot difference as significant, however.

5.) Most light GA aircraft are equipped with 2-12 volt batteries connected in series. Are these considered 35 amp-hours, meaning will they run 35 amps for one hour or 70 amps for half of an hour? I am trying to gain a better understanding of how much I can run off the bat in case of alternator failure?

Voltage and amps are two different animals. If you have a 35 ampere-hour battery, then your statements are correct in that it will give you 70 amps for 1/2 hour or 35 for one hour. Connecting 2 12 volt batteries in series will yield 24 volts, but how many amps that is depends on how big the batteries are.

 

[Mickey]

1. No! If either your beacon or any of the strobes are inop you cannot operate day VFR except to fly to a location to have it repaired. 91.205(b)(11) ...In the event of failure of any light of the anticollision light system, operation of the aircraft may continue to a location where repairs or replacement can be made.
I think the beacon would fall into the 'any light' category.


5.Your understanding of amp hours is correct
Putting two like batteries (or cells) in series will double the voltage but the amperage will stay the same. Putting two like batteries (or cells) in parallel will double the amperage but the voltage will stay the same.


Take care.

 

[groundpointsix]

1. No! If either your beacon or any of the strobes are inop you cannot operate day VFR except to fly to a location to have it repaired. 91.205(b)(11) ...In the event of failure of any light of the anticollision light system, operation of the aircraft may continue to a location where repairs or replacement can be made.
I think the beacon would fall into the 'any light' category.

I believe that the strobes and the anti-collision lights are considered two seperate systems. If you read 91.205(b)(11) again, you will see that it says you must have "an approved aviation red OR aviation white anticollision system." Therefore, if your strobe (or your beacon) fails and you still have the other system operating, you're legal. Now, if you're flying an older 172 that had the strobes installed aftermarket and wired to the same switch as the beacon, it might be a different story under certain circumstances (i.e. a short circuit), but a burned out bulb in one light shouldn't make you illegal. That's what I was taught from the beginning-- that I needed one or the other, but not both. If someone has a legal decision saying otherwise though, I'd love to see it posted, especially since I just made a flight with inop strobes this morning.

 

[safepilot24]

The way I understand it is that the anticollision light system means either beacon or strobes. Since the regs do not specify "beacon" or "strobes," if my beacon became inop my strobes make me legal. Perfect example is Archers and Mooneys do not have beacons. I think this is a reasonable way to look at it. But listen to me rambling about beacons when we are on the brink of war...!
B

 

[Kream926]

i believe stobes count as an ati-collision lighting....im pretty sure you van use strobes if the becon is inop or not installed..

safepilot24 i belive as a CFI you should know these things..if one of your students asks and you dont know the answer your not doing your job

 

[avbug]

Most light general avaition airplanes don't have two batteries. The 35 amp-hour battery should (in theory) deliver 35 amps continuously for one hour, or one amp for 35 hours, etc. This applies to a new, fully charged battery with specific gravity in the designated range for the fluid temperature.

Which is worse, a slipping or skidding spin? Think about that for a minute...think about the spin, the aerodynamics and forces involved (speaking in general terms here), and the recovery.

Can you have a slipping or a skidding spin? Remember that a spin is a rolling and yawing motion, and frequently a pitching motion, coupled, but not linear in their relationships. Think about the relationship, and you'll realize it's a "trick" question.

Entries are another matter, and I suspect the person doing the asking is one who subscribes to the cross-controlled-stalls-are-evil school of thought. It's a fallacious school of thought, but a popular one. It's borne of too little cross-controlled training...ask the question here, and you'll find that a good number of responses will probably be that you should never do a cross controlled stall...mainly by those who are missing some very basic flight training and skills.

People are getting asked this on their practical test?

 

[Iceman21]

I have flown with the beacon inop during a night flight, I inquired about it, looked up the exact reg and talked to our chief instructor. The beacon was placarded and the strobes were working just fine.

LEGAL!!!

I would love for an expanded discussion on the spin theory avbug mentioned. Would you oblige?

 

[172driver]

The spin itself will be no different once developed. However, the slipping entry (cross-controlled) is a bit more aggressive as the high wing will stall first and drop all the way through. A little surprising the first time you perform it but no more dangerous at altitude than a skidding entry.