問問題~

hi~ @Mja Thanks for your questions~ I m looking for a proper way to explain to you in a simple way~

will reply later~ Cheers~

Hi~ @Mja

As altitude increases, air gets less dense.

Less air molecules goes across the airframe(less friction), therefore, as altitude increase, parasite drag will decrease. However, since the air is less dense, the AOA has to be increased to compensate, which also means the Induced drag will be increased. Therefore, the Vx and Vy will move to the right on the Chart. (Vx and Vy increases)

Also, HP avail goes down as the engine and propeller performance got affected by air density. Therefore, as altitude increases, the excess HP avail is reduced. (climb rate will be reduced even with Vy.) Picture credited to Boldmethod

I replied on the Tech page~

you can check it out~ https://bit.ly/Forces_on_Prop

@Dream to fly

Good question and very technical question!

1) when in unreliable airspeed with all 3 pitot tubes fails (What a bad luck), procedure will call for BUSS Backup Speed Scale for us to fly.

Since we wont have pitot static information, it will provide relative info from AOA.

It looks like the picture on the right. It provides us a margin to operate within parameters.

(very technical stuff)

As I recall, ATR doesn't have such feature. I am trying to find out if the new -600 series has some updates on system.

ATR unreliable speed MEMO item

2) We can also use the GPS info to get an idea about our speed and altitude. Of course, not super accurate, but when all 3 pitot tubes fails on you, you need it.

3) In a small GA aircraft, you will be lucky to fly with an GPS equipped aircraft. Usually, it is more expensive to rent and operate.

In case, your pitot static is all blocked, and you don't have a GPS onboard; there's also a way to get those info.

Use your ATC, declare your failure(if you are in radar covered environment) you can ask them for your Ground speed on radar.

Just a question back to you guys:

In a GA aircraft, In case you have a static port blockage, what will happen to your indication? and how would you fix it?

(it is a question for whoever sees it, Comment below and check your understanding!)

@ATVpilot Static Port Blockage, Altimeter indication becomes freeze and unreliable.

Since ASI measure dynamic pressure by comparing the total (pitot) pressure collect from the pitot tube and static pressure collect from the static port, without a reliable static pressure source, airspeed indicator becomes unreliable too. In climb, airspeed indicator will under read due to decrease in static pressure. In decent, airspeed indicator tend to over read because of increase in static pressure.

In addition, vertical speed indicator will also become unreliable. As static pressure source in the pitot-static system remain constant during climb and decent, VSI will return to zero reading soon after the static port became blocked. (Takes a while for the air pressure in the VSI case and capsule to be equalised.)

Pilot reaction to static port blockage as follow,

First, fly the aircraft, maintain a straight and level (or a stable) attitude with a sufficient throttle power setting before commencing any further action to the failure.

Secondly, after confirming the failure caused by static port blockage, switch the static pressure source to alternate. This action will let the cabin air entering into the static pressure source of the pitot-static system. For older aircraft type without an alternate static pressure source, pilot may attempt to break the glass shield covering the altimeter by using a sharp/hard object to let the cabin air flow back inside to the instrument and pitot-static system. Be nice and gentle when breaking it (expensive instrument though).

Note that the altimeter will be slightly under read when using the alternate source since cabin air pressure is a bit higher than the ambient pressure outside. ASI could be under read by the same reason but the rate is so small and generally be neglected. The VSI is unreliable.

Understood, thanks~~另外其實再想問少少instrument flying嘅野，entry a holding pattern有三個way，direct, teardrop, parallel，你會用咩方法去記邊個角度飛邊個entry？

@Dream to fly

Thanks for your good question again!

So holding pattern has 3 entries:

Direct/parallel/teardrop

Standard holding pattern 係right turn.

咁我個techniques 係：

1) fly toward the navaid(初學者用VOR 做)

2) right turn right thumb;

Left turn left thumb

放係個heading indicator 度。

隻手指公會separate 左teardrop 同direct sector.

3) 睇下你個holding course 喺邊個sector.

E.g. base on the picture above.

Current heading 120⁰

required to hold at the fix in front

020 radial right hand turn.

020⁰ falls on "parallel" sector

so it is a parallel entry.

呢個我IR 玩左好耐！如果早d 有人教我呢個technique, 我慳唔小groundschool 錢！

都係嗰句~唔明要問！唔使怕羞~