Had commentators asking about the P-9 and it's unducted fan (UDF) or "propfan."
"Sounds really loud - wouldn't a sub hear it?"
Submerged submarines can detect aircraft or helicopters overhead in some instances. But that has a lot to do with the type of propulsion system used.⬇️
From physics first principals, it's easy to deduce that sound emitted by low-flying aircraft can hit the surface and be transmitted into the ocean. There are many open source references talking about it in theory and practice.
But like anything having to do with sound propagation and passive sonar, the type of signal has a lot to do with how easy or hard it is to detect. A signal that maintains a constant frequency will be easier to pick out than one that varies frequency or spread across a frequency band.
A constant speed turboprop - like those that power the P-3C - have the turbine and propeller spinning at constant speeds, with the propellers varying blade angle to adjust thrust higher or lower. This creates a very well-defined signal, even if the aircraft is not particularly loud overall.
A turbofan MPRA aircraft - like the Nimrod, P-1, or P-8 - uses engines that vary the speed of the fan and the compressor/turbines to change thrust levels. As a result, there will always be large or small variations in frequency - making the sound signal harder to detect - even if it is louder from a radiated noise perspective.
So would the UDF have been extremely easy to detect underwater by a sub? In short - I don't have a way to say. We would have to find some of the engineers or get some high-fidelity recordings of the engines where we could analyze the sound spectrum.
The worst offender from being detected while airborne? Probably the Russian and Indian Tupelov Tu-142 Bear-F ASW aircraft. Four massive Kuznetsov NK-12 turboprops generating ~14,800 HP each and turning 18' diameter contra-rotating props. Extremely loud aircraft combined with constant speed propellers. Would probably hear them coming from a mile away.
📷 @covertshoresBsk and Fedor Leukhin
11 years ago today, Malaysia Airlines MH370 disappeared during a flight from Kuala Lumpur to Beijing. My crew and I were deployed in Japan - and we took part in the search. This is the story of the first few days of one of the largest airborne searches in history. (1/17)
This may help & please, can at least the reliable members stop spreading nonsense on J-10CE deliveries to Egypt & Sudan alike?
The Chinese Ministry of Defense spokeman Wu Qian said that deliveries of J-10 fighter to Egypt are completely fake news.
It's all made-up by fan-boys.
Filipina hendak datangkan 40 unit F-16 Block 70 Viper.
Kementrian Pertahanan Filipina dikabarkan tengah dalam negosiasi dengan Pentagon untuk bisa membawa pulang F-16 variant tercanggih saat ini, F-16V Viper.
Filipina juga kebanjiran Bantuan Militer sebesar 500 juta USD dari AS
#OTD in 1995: A USAF F-16 [89-2035] is shot down by a Bosnian Serb surface-to-air missile while on a NATO patrol flight over Northern Bosnia. Pilot Captain Scott F. O’Grady, ejected safely and evaded the enemy for six days until being rescued by US Marines. #aviation #aviationdaily #aviationsafety #aviationhistory #avgeek
"Bahkan impian Aditya menjadi pilot tempur TNI AU tidak pernah kesampaian karena dipapras begitu saja oleh sang ayah karena tau akan mendapatkan privilese nantinya"
"Hoegeng menyuruh Aditya (putranya) menyambangi kantor ayahnya di markas Polri Trunojoyo, untuk diminta tidak masuk ke Akabri Kepolisian karena ia tak ingin ada dua Hoegeng di Korps Bhayangkara"
-Tempo
On nous demande régulièrement quel est le processus de création des livrées Rafale Solo Display (RSD) ou commémoratives des avions de l'@Armee_de_lair.
Prenons l'exemple de la dernière création du RSD, cas relativement simple dans son déroulement :
A stunning view of a Kazakh AF Su-30 in a gentle bank. With 37 Su-27/30s in "active" service and 16 more on order, #Kazakhstan ranks among Central Asia's largest operators of Flankers. Compared to the pilots, look at the size of the aircraft! It's huge. #avgeeks