Today we will talk about the Mach speed and its indicator located inside the cockpit in all types of aircraft.
some time agoúIn a while I had the courageíto answer a question about the importance today ofía of the indicationón and número MACH. Obviously the comments were not long in coming from many commander pilots.óyou see what I oweíeven though I don't haveíno idea what he was saying; which doesn't surprise me; what did surprise meó, y muchísimo, was that other veteran pilots, spaghettiéThey didn't think the same and didn't understand what I wantedíto say.
Post written by: William Casalins
Aeron Engineeráuseful
Foundationón SON
The answer was: “currently it is useless, what serviceía más that all to browse” and I felló the aeron communityáutica above (including fighter pilots), except for one or another pilot who knowsíexactly what I was talking about let's see if I'm wrong.
The speed of sound and the shock wave
The númere Mach is the relationón between the true speed and the local speed of sound. This is an expressionón dimensionless velocity, así that at a speed of Mach 1.0 goes to the local speed of sound. The speed of sound at sea level is equal to 662 knots (in the air). Mach 0.8 at sea level corresponds to a true speed of 528 kntos (o Mach 0.8 equal to 528 torn between 662 knots). The speed of sound in air decreases with altitude due to the decreaseón of temperature.
Although the avión fly at sub speedsóunique, in some portions of this (especially of the wing) may be moving at super speedsóunique (as shown in the figure 2) it's ahí where the famous shock wave is produced that destroys part of the liftón, creates great aerodynamic dragámica and so onás stability problems. It's from thereí that the arrow wing is born that is really used to make the “noneñor of the century” to the relative wind at high speeds
All this has great value for designs.ñaviors and buildersón. For the pilot it is a knowledge más of the máquina and its performanceñO. ¿Cuál caníto be your additional utility? One peróximos capíresult podríwe love to talkáI just know this (in the language that any Airplane Hobbyist could understand)
mach indicator
Engineers scrambled to make innovations so the pilot would have less work to do, they put an autopilotátitic and almost nothingíto nothing, then I due themñthe aerosolsíneas told those who didíeven the planes: “hey, póGive them the work of the navigators since these men(the pilots) they don't do anything anymore” (my friendían put Part of work you doían los radio- operators, making radio equipmentás fáeasy to use; and if, radio aids They gave the final blow to the sailors. Now with the G.P.S. and navigationón for satélite, who knows whoén be next. We already know that the position of the flight engineer (con tanta automationón) notó to a better life. The dueñMost companies believe that their employees do not do enough and every time the engineers make progress and remove a crew member, they jump for happiness (one less union to deal with) and a salary less to pay. Soon we will see passenger planes with only one pilot.
The Mach indicator that related true speed to the local speed of sound and toldía al piloto la ground speed (G.S.) no need for a calculator (if the wind was calm). A notable advance for the élittle.
Actually the Mach indicator in sub flightsóNicos indicated a percentage of the speed of sound at that height. For instance, if the indicator shows .80 that means you go to 80% of the speed of sound at that height, but ¿cuál is that speed of sound?
¿I mean, what is it for you? Because if it is so that you do not pass at dangerous speeds (that they are) They put an indicator on the instrument (barber pole, that changes with the factors that affect it) so that you do not reach él and do not exceed it, además of certain alarms that sound when cr speeds are exceededíethics.
indicated speed
It is the speed of the planeón with respect to the air that surrounds it and is obtained by a device that consists of din intakesámicas , Eastáethics and an instrument that shows them to you in a measure that you can interpret Knots, Km/h. etc. .That's what the performances are based on. grandfather'són and limitations, We already know that air behaves under certain circumstances like an incomprehensible fluid., However, as speeds and operating heights increase,ón already begins to behave differently and the performances and behavior of the aircraftón changes ,obviously the equipment that works with that ambient air alsoén. At low flight levels, the speeds shown by the instrument and the real ones with respect to the ground were very similar, as you rise and goás ráI ask for those speedsíwere still going to be very different and was no longer a reference for navigation.ón.
true speed
We already said that the indicated airspeed and the true airspeed are very similar at low levels of flight., in the formula, we can notice that as the ALT becomes más smallñto or is equal to 0(at the sea level) the I.A.S. They are very similar or the same as the T.A.S. then it becomes a good measure to know whaté speed I am moving on the earth and predict how long it will take me to reach my destination, we must remember that the fuel that keeps us in the air is not eternal, y así make a cáCalculation of how far I am going to travel before being left with empty tanksíI hope the night catches us in a visual flight.
TAS = IAS + (0.02IASxALT/1000)
It is very desirable to know at all times the true speed that gives us the main data to calculate our estimates..
Ground speed
We must remember that air speed and ground speed are not always the same., in fact, hardly ever, but at low altitudes and with calm wind those speeds are quite similar. Al avión cares little about speed over the earth, a éHe only cares about the speed with which the air passes throughés of its wings and control surfaces and demás parts. But to the pilot yes and to the ground controller too.én (especially before there was noíto such sophisticated radars) to make their estimates and the other to make their ordering of tráI'm theéreo.
Examples
How an image is worth máI know a thousand words an example is worth moreáI know that 100 explanations.
Let's suppose that we are flying to 32000 feet tall level 330, the speedímetro me indica 291Knots, I want to know whatáHow long will it take me to travel 80 miles náutics that the D.M.E of a station shows usón.
We take out our calculator or our flight computer and it gives us.
- T.A.S. = IAS+(0.02 IASxALT/1000)
- T.A.S.= 291+(0.02(291) x3200071000) = 291+186=477 miles/hour
- 477/60=7.95 miles per minute.
- TIME =DISTANCE/SPEED
¿Whaté marketíand you are: we look at our MACH indicator that marks us 0.8, we move a point, and we divide it to what the D.M.E.?
- TIME =80Miles/7.95 (miles/minute) = 10.06 minutes.
GPS.FMS
Countless navigation systems have been invented.ón getting better than the last, now you can surf satélite and with an error of a few meters, all the informationón what you need and (the one that doesn't) spaghettiéYou can't get it in real time, on your own phoneésmart phone and on the avión, the manuals, the systems, checklists etc.. You can never get lost anymoreás, the compañíto twoñto the ancestorsón follows your trail, can you send the problemséaircraft cynicsón long before landing and everything we never imagined a few dayséregistered behindás. You get on the planeón, manages from the fly, you relax and look at the landscape.
Conclusions
At first I flewáWe were only going with the indicated speed and from thereí all limitations were taken, at low altitudes, this was very close to reality and as all the flights were visual, no había ningúno problem. MáIt's late it startedó to fly más alto y más ráI ask, I no longer matchíeven the speeds andíwhat to do “complicated” cácalculations for approaching instrument flights (for long flights, navigators were needed) so the engineers (who never sleep) they invented an instrument that gave you the true velocity on the instrument, you only needed a DME distance and a watch to make your estimates. Aun así, it was too much work, and then those “infamous “Engineers improved the equipment and GPS was invented that gave you speed and position.ón real, the wind component and the estimate just by looking for a desired point. But stillí They were not satisfied and then they put youíeverything on a big screen, to the avión they drew it on a map in real time on a path to follow, taking all this into account, ¿Can you tell me what your MACH indicator is used for today?, knowing that you have alsoás an IAS indicator, which is equivalent (for performance and flight limitations) and that all the flight data about navigationóYou don't have them resolved on a map on a screen?
In this picture, among many thingsás, the T.A.S tells you. (479) and the G.S.. (482) which means you have a tailwind component of 3 Knots
postscript
I am not a pilot, I am a flight engineer, and flying CARAVELLE, a free throwés, one takesán instructor, Major JAIRO GARCIA taught meñor all this that I am telling you now, the co-pilots and some commanders (on éfew that do not existíto the GPS) he was surprisedíeven as he gave them the times for the descent and the exact fuel data. In fact, I'm not belittling the mach indicator, on the contrary, I am stating that in a élittle was underutilized by some aviators who didn't understand itístill completely. Say algaeún pilot has something that añhill, welcome the contribution.
I want to thank you for the collaborationóby Yerson Leonardo Angarita
All drawings and photos were obtained from Boeing
