Who's Online

We have 1325 guests online

Live Traffic Feed

Life in the Skies

'A Local Bestseller!'

What Tony says
(See here)
and Book Launch video here
 
What others say

Les Posen
(See
here)

Yvonne Lee
(See
here)

Louisa Lim & Allan Koay
(See
here)

Aireen Omar, Asran & Bo Lingam
(See
here)

38 Readers' Comments
(See here)

Get an autographed copy here

AMAZON.COM  -  To Order, please Click here 

(eBook) Kindle edition - please Click here

Latest Comment

What are the cruisin
"how in the hell can you reach JFK if you leave fr

What are the eyesigh
tjsoihsdojfsioufs f post

What are the procedu
Hello Sir, I am currently B737NG Cpt.TRI /TRE hol

Could an A320 pilot
I plan to do ATR 72 -600 type rating , for that be

Is there less turbul
Flying from San Francisco to Philippines, end of M

What you have to do
Hi Capt . Im a grade 12 student and i really want

Does a jet aircraft
Earth is flat.

What factors lead a
Hi Captain Lim! Thank you so much Sir, you enligh

What do you think ab
i am from Taiwan, now planing to PEA, but after re

Etihad Airways Cadet
hi sir i am Ashutosh mahajan from india and my dr

Paperback Version

 For Local Availability - Check Here
 
Home > Flying the Plane > What is the gliding speed of a commercial jetliner and what is the range of the ELT?
What is the gliding speed of a commercial jetliner and what is the range of the ELT?
Flying - Flying the Plane
Tuesday, 27 October 2009 15:10

Dear Captain Lim,

I’m just wondering, generally what is the gliding speed (with total engine failure) of a commercial airliner eg A340 or B777?

I have heard so much about ELT being picked up by aircraft say flying at 28000 feet. What is the formula for calculating the range of the ELT?

When is the signal heard or signal lost? Roughly, what is the distance apart between signal heard and signal lost? Is this distance fixed?

Thank you.

Charlie Yen

Hi Charlie,

The best gliding speed of any commercial jet liner is the speed that gives the best “lift/drag” ratio. Yes, a plane can glide at any speed following total engine failure as long as it is not below the stalling speed. But there is only one speed that gives it the maximum gliding range. On the Airbus, it is the “Green Dot” speed indicated on the airspeed indicator.

Following total engine failure, the recommended gliding speed for both the Airbus A340 and Boeing 777 is in the region of around 250 knots. But remember, this is not the speed to fly at initially as the pilot would want to attempt to relight any failed engines in the air. So they prefer to glide at 300 knots, hoping to get the engines started until it becomes hopeless whereby they would then fly at the best gliding speed to reach a good spot for a prepared crash landing.

Please see my previous article about glide landing on a jet here.

The ELTs (Emergency Locator Transmitters) are installed on planes to enable others to detect their location in the event of an emergency crash landing in jungles or water.

How far then, can a plane be located if it crashed into the jungles and the ELT is activated? Well, you can use this formula for calculating the theoretical VHF reception distance in nautical miles: 1.23 multiplied by the square root of the altitude (feet). If the plane were at 28000 feet, that would be around 205 miles.

In practice, the actual practical range is generally around 10% or less than this, depending on transmitter power, the effect of terrain and how good the receiver is. When submerged the ELT’s range is quite drastically affected, since the water absorbs radio waves.

However, I believe the ELTs are equipped with an acoustic "pinger" that runs for 30 days that can be received by acoustic sensors for a long distance in water, since water transmits sound well.

The duration of the ELT is around 48 hours and should be heard if a rescue plane is within the range. Obviously, the power of the transmission weakens as the battery runs low and the distance of the reception will deteriorate as well.

P.S. My apologies to many readers - I have not been answering any questions lately as I was very, very busy.

Trackback(0)

TrackBack URI for this entry

Comments (1)

Subscribe to this comment's feed
MD-83
WHAT WILL BE THE SPEED AND GLIDING DISTANCE WITH ENGINES OF AN MD-83 .?
ERLYN GONZALEZ , 09 Oct, 2010

Write comment

smaller | bigger

busy
 

Paperback Version

 For Local Availability - Check Here

Recommended By..


LIFE IN THE SKIES

'A Local Bestseller!'

Recommended by

Patrick Smith
Boston USA
(See
here)

Capt Meryl Getline
ex-United Airlines USA
(See
here)

Capt Doug Morris
Canadian Airlines
(See
here)

Capt  Robert J Boser
ex-United Airlines USA
(See
here)

38 Readers' Comments
(See here)

Get an autographed copy here

AMAZON.COM  -  To Order, please Click here 

(eBook) Kindle edition - please Click here

View Book Launch video here

Follow me

@CaptKHLim

Like What You Read?


If you like what you read, more stories are found in my book LIFE IN THE SKIES (Preview here) and you can purchase a copy here. To check for any latest updates or postings, you can follow my Twitter at @CaptKHLim or Facebook here

MH 370 Interviews

Click here to View

10 Most Popular Posts



Disclaimer | Privacy
2004 - 2011 © AskCaptainLim.com | Site Concept by eQuilec.com