Speed Transition (IAS - Mach)

[@DrPankajMalukar]

Thank you Capt. As usual very informative video. Thank you for sharing your knowledge & practical tips that can not be learnt from the books!

[@AbdulmuatiAsiri37]

You are most welcome And thank you for your kind words 🙏🏼

[@rafaelcarvalho6222]

Returning to the flight deck after the pandemic now. Thank you for all the videos.

[@AbdulmuatiAsiri37]

Glad to hear it Rafael, that you are returning back to the flight deck, Have fun flying Let me know if you have any questions All the best Abdul

[@diegobeatrice5257]

Hi, very cool video. To add some additional information to your video, the IAS is a measurement of the dynamic pressure exerted by the air molecules entering the capsule of the instrument via the Pitot tube and it is dependent upon the velocity at which the airplane moves through the air or TAS and the air density determining the number of molecules in a given volume, and can be mathematically expressed by the formula IAS=TAS x rho where rho represents the air density: thus as the airplane climbs at a constant IAS as the air grows thinner the TAS must increase in order to maintain a constant value of IAS. On the other hand the Mach number represents the ratio of the aircraft velocity to the speed of sound or LSS Local Speed of Sound which is turn is given by the formula 39 x square root of the temperature in degrees Kelvin: the formula for the Mach number is TAS/LSS: once again as the airplane climbs at a constant IAS as the TAS increases while the LSS decreases as the air gets colder, the Mach number increases up to an altitude referred to as change over altitude where if the airplane continued to climb at a constant IAS it would reach the critical mach number and eventually exceed the aircraft limitations and thus the airplane is flown with reference to its Mach number. When climbing at a constant Mach number as the temperature decreases the TAS must be decreased as well in order to maintain the TAS/LSS ratio constant, besides as the TAS decreases and the air density decreases as well the IAS decreases especially above the tropopause at 36000ft where the decrease in pressure is no longer compensated by the decrease in temperature. During the descent at a constant Mach as the air gets warmer and the LSS increases in order to maintain the TAS/LSS ratio constant the TAS must increase as well resulting in an increase in IAS until the IAS catches up with the target IAS and the descent is continued with reference to the IAS rather than to the Mach. I hope it clarifies things up for those who are not familiar with the concepts of IAS, TAS and Mach number. Once again thanks for sharing and looking forward to the next video.

[@AbdulmuatiAsiri37]

Hello Diego, What a great way of explaining it, thank you. You really dos clarified it for me as well. Thanks again 🙏🏼, well explained All the best Abdul

[@diegobeatrice5257]

Abdulmuati Asiri thanks a lot, i just wanted to add something to your video for those who are not familiar with the IAS and Mach number

[@AbdulmuatiAsiri37]

That was great Diego, I admire your level of technical knowledge please do continue to share, that is how we all help each other improve and grow. And I am dead serious when I said your explanation made it clear for me as well. It has been along time since I studied this information. Thanks again😊 Abdul

[@daddinhaydarov8393]

What a great explaining. Another way of memorizing is using your fingers, where little finger= IAS, Ring finger= CAS, Middle finger= TAS and Index finger= MACh. So when you keep your little finger(IAS) straight , other three goes to the right (from bottom to top) which means CAS,TAS,MACH INCREASING when climbing. While descending if you keep index finger straight(MACH) other three again goes right (from top to bottom) meaning descending at const MACH, IAS, CAS,TAS will increase. Hope it helps to memorize. Thank you.

[@AbdulmuatiAsiri37]

Hi Daddin thanks for the input, I am not sure I understood this way can you explain it differently please. Thank you Abdul

[@ATPLStudent]

You cover excellent topics captain thank you for sharing, jazak allah kheir

[@AbdulmuatiAsiri37]

It's my pleasure

[@mtrackerbeyond]

Very informative video Captain, once again you have enlightened me. Thank you for the time you take making these informative videos.

[@AbdulmuatiAsiri37]

Helloooo my old friend. Thank you mtrackerbeyond for your constant support for the channel 🙏🏼

[@shkhan9375]

Very nice and helpful video sir. This is my first video from your channel

[@AbdulmuatiAsiri37]

Glad you liked it 🙏🏼

[@user-wl6bw3jl4n]

Thank you Captain Asiri for this informative video. Safe flying always.

[@AbdulmuatiAsiri37]

You welcome Chris, appreciate you taking the time to leave a comment 🙏🏼

[@daddinhaydarov8393]

Great video, Captain Asiri.

[@AbdulmuatiAsiri37]

Thanks Daddin 🙏🏼🙏🏼🙏🏼

[@syednaveed5521]

Thank you Cpt. As always really wonderful and deeply informative videos.

[@AbdulmuatiAsiri37]

Thank you Syed, I really appreciate your kind words 🙏🏼

[@obasaran35]

Thank you so much Captain. Another great video.

[@AbdulmuatiAsiri37]

Appreciate you taking the time Onur to leave a comment 🙏🏼

[@ipw68]

Yes very valuable information again! Thanks!

[@AbdulmuatiAsiri37]

Thank you Inge 🙏🏼

[@elmestamekhalil2969]

thanks sir that was perfectly explained i have a question as an atc when i instruct a pilot to maintain an specific IAS this last becomes the targeted IAS many thanks

[@AbdulmuatiAsiri37]

You are welcome EL MESTAME, The pilot will have two options, either to change the target speed in the FMC or open the speed window and do it that way. Hope that answer your question, Let me know if you have any other questions All the best Abdul

[@elmestamekhalil2969]

@@AbdulmuatiAsiri37 much appreciated

[@Aziz-qn8cv]

الله يقويك ياكبتن ماشاءالله عليك محترم وفاهم وعارف وش تقول . ممكن اعرف ياكبتن ايش الشركة الطيران اللي تطير فيها . بالتوفيق ❤️

[@AbdulmuatiAsiri37]

الله يسلمك ويعافيك، اعتذر منك عن ذكر اسم الشركة، حتى يكون محتوا القناة مستقل، شكرا لك على كلامك الطيب 🙏🏼 وتمنياتي لك بالتوفيق والنجاح عبدالمعطي

[@koolmoin92]

Hello Captain, I loved your series on V/B, I have a query that in FCOM II, under chapter 4>control and indicators (10)>C/O switch, it is mentioned that automatic change over occurs at FL260, why is there a FL mentioned here, is it related to something else?

[@AbdulmuatiAsiri37]

Hello Moin, Thank you so much for the comment. You are right it is mentioned FL260 is where automatic changeover happen. To be honest with you, so far I am not sure what does that mean exactly, as from what I have observed so far, the changeover does not happen at an altitude if VNAV is engaged, and if the speed window is open the changeover will happen near the limit of the speed. Next time I fly I will open the speed window while VNAV engaged and see if it will changeover from mach to IAS or the opposite near FL260. Again thank you so much for the comment. Please let me know if you have any other questions or comments. All the best, Abdul

[@AbdulmuatiAsiri37]

Hello Moin, After your feedback regarding the mention of FL260 for automatic C/O, I was thinking about, guess what if VNAV is engaged and the speed window is open, the change will happen at around FL260 regardless of what the target is both in the climb and in the descend. If the speed window is closed then VNAV will revert to the logic I mentioned in the video. Thanks Moin you pushed me to explore this, and learn something new. 🙏🏼🙏🏼🙏🏼. All the best Abdul

[@koolmoin92]

@@AbdulmuatiAsiri37 Thank you captain, it clears the working behind the change over at FL260, I too will try it on my next flight. Thanks and stay safe captain.

[@AbdulmuatiAsiri37]

No Sir thank you, you have no idea how long I was thinking about it (I am talking like years), and when I saw it last night in the flight I was happy like a kid eating candy. So THANK YOU VERY MUCH 🙏🏼

[@relaxdud200]

thank you captain asiri

[@AbdulmuatiAsiri37]

You are most welcome dear Andy 🙏🏼

[@aarndub0760]

What should i do if for example they say 250kts on conversion

[@AbdulmuatiAsiri37]

Hi, Am assuming you are receiving this instruction on descend, If that is the case, - Either go to the descent page in the FMC and in the speed put /250,,, the FMC will take care of it,,,, - Or as you descend and as the indicated air speed start to increase as soon as it become 250 that is actual indicated, open the speed window change over to indicated and use any descent mode you like. In either case remember that you need to descend early so keep that in mind. Hope that answer your question, All the best Abdul

[@kishansn3145]

Thanks a lot

[@AbdulmuatiAsiri37]

You are most welcome Kushan 🙏🏼

[@SaurabhKumar-hr7fn]

Can you also please explain the concept between IAS, TAS and G round speed? Thanks

[@renzomartinez3351]

Airspeed transition/mach transition. The point where you use mach as reference instead of airspeed.

[@AbdulmuatiAsiri37]

ISA the speed you see in the speed tape, it is computed through measuring the air pressure in the pitot tube. As you climb higher, the air becomes thin the speed tape may indicate low indicate air speed but in reality the air plane is flying very fast though the air “with respect to the air” that is where TAS comes in play a system in the airplane will do all kind of computation to present to you the actual speed the airplane is moving through the air. Ground speed is that how much distance over the ground the airplane is traveling per hour. If you take the TAS and add the value of the tail wind if you have tail wind or subtract the value of the head wind and you will get the ground speed. Hope that answer your question. Let me know if you have any other questions. All the best Abdul

[@Zaur-ue1zh]

Vertical deviation more than 3000 feet why fma readout fmc sped / lnav/Vnav pth instead of arm /lnav/ vnav spd ?

[@AbdulmuatiAsiri37]

Hello Zaur, The airplane is in DES NOW mode, so the VNAV is descending at 1000fpm and maintaining the target speed in the FMC. The throttle is constantly adjusting to maintain the target speed at 1000fpm sink rate. Hope that answer your question. All the best Abdul

[@SaurabhKumar-hr7fn]

I have another question Captain. If ATC asks for a good rate of climb while I am in Mach, should I climb with indicated or Mach number? If I fly with constant

[@AbdulmuatiAsiri37]

Hello Saurabh Kumar, I believe the comment was cut for some reason if you "fly with constant..."? What I personally do is to go the CDU clime page and select max clime, and either let VNAV do it or open the speed window and select the suggested speed by the FMC. As far as weather to do it in Mach or indicated I will do the same logic mentioned in the video, if Max rate clime speed now is what I am flying in Mach then Mach, if it is Indicated I will use indicated. Hope that help Let me know if you have any other questions. All the best Abdul

[@alexmp3821]

Question, I see you keep 290 ias while climbing, if I pass level 20,0,, Can I increase it to over 320 ias?

[@AbdulmuatiAsiri37]

Hello Alex, As you climb IAS will decrease, meaning the red bar will get closer to a lower indicated speed the further you climb. So you might be able to use 320 IAS at the initial phase of the climb but then you will need to change over to Mach No. to make sure you don't exceed the speed limitation. Hope that answer your question. All the best Abdul

[@alexmp3821]

@@AbdulmuatiAsiri37 yes thank you

[@SaurabhKumar-hr7fn]

Captain, I have a question- why is it that you were constantly climbing at target 290 speed indicated and suddenly the speed drops on the indicated scale?

[@AbdulmuatiAsiri37]

Hello Saurabh, As you climb the air get thinner, the indicate airspeed will drop cus their is not enough pressure in the pitot tube to be able to compute an accurate indicated air speed. At around 29,000ft everyone start to use Mach number which is related to the speed is sound in the air. Hope that answer your question, All the best Abdul

[@SaurabhKumar-hr7fn]

@@AbdulmuatiAsiri37 Thanks Captain. Can You then explain how the relevance of TAS and how it is computed? For nav purpose, are we using TAS or Ground airspeed?

[@AbdulmuatiAsiri37]

Very good questions Saurabh, I will look into it, To be honest with you I don’t remember using either one,,, been relying on the FMC a lot 😕