Everyone today looks upto India as the next destination for growth. The Ministry of Civil Aviation, in its draft National Civil Aviation Policy, has captured the attention of everyone with the claim of a large middle class population, and the promise of certain reforms that should may better the ease of doing business.
We appreciate what the Ministry has done, is doing, and will do. But certain claims must be taken with a pinch of salt, must be questioned, and analysed, just to prevent over-optimism and to make room for realism. Like for example:
India is a 300 million strong population of middle class persons. The Ministry targets each of these 300 million to fly atleast once in their life. Pertinent questions: What is the definition of middle class? What subset can really afford air travel? These questions are important to prevent overcapacity in the Indian market based on optimism.
India targets 300 million domestic ticketing by 2022. That means, calendar year (CY) 2021 must end with 300 million domestic passengers in a single year. India will end CY 2015 with 80 million domestic passengers. What is the compound annual growth rate (CAGR) required to touch 300 million in CY 2021? Is this CAGR too high to achive? What do market leaders like Airbus say?
Today, we focus on these two issues, which form part of the Ministry’s vision, and we see if this is achievable. Our views on the Regional Connectivity Scheme and the 5/20 are ready, which we hope to release tomorrow. We will also be commenting on Scheduled Commuter Airlines (SCA) and Safety, and lightly touch upon Aeronautical ‘Make in India’, Aviation Education & Skill Development, and Air Navigation Services.
To read about the first two issues, please click here.
DGCA published data pertaining to an airline’s performance, commonly quoted by the media, such as Load Factors and OTP, is unreliable and misleading.
The data errors can only be recognized in single fleet airlines and/or airlines that have only recently started operations. In both cases, simplicity allows for cross verification of data.
Investigation into the data errors was suggested by a senior officer of a full service Indian airline.
The most interesting of all airline performance indicators is load factors. Load factors are often looked upon as indicators of successful commercial operations at an airline.
DGCA publishes certain airline related data based on an ICAO (International Civil Aviation Organisation, a UN body) ATR (Air Transport) ‘FORM A’. This form is filled and submitted by airlines to the DGCA, which the DGCA then uses to report load factors airline wise.
The manner in which the DGCA computes load factors is by dividing Passenger-Kilometers (PK) by Available seat Kilometers (ASK). PK is a product of total passengers flown and the total kilometres flown by the airline in a particular month. ASK is the number of seats on all flights multiplied by the total kilometres flown by the airline in that particular month. Dividing PK by ASK simplifies to the ratio of Passengers Flown by Available Seats, which is the definition of load factor.
Another way of computing load factors is to determine the available seats using data not reported in ICAO ATR FORM A. This is the number of seats on every flight. FORM A mentions the number of departures in a month. In single fleet airlines such as IndiGo, Go Air, AirAsia and Vistara, the number of seats on every aircraft is uniform fleet-wide. This means that every flight on each of the above mentioned airlines flies 180, 180, 180 and 148 seats, respectively.
Multiplying the number of flights by the number of seats per aircraft will result in the number of seats flown in that month. Dividing the number of passengers flown by the number of seats gives us load factors for the month.
The first and second method should result in the same numbers. However, this is not the case. Below is the reported load factors versus the computed load factors for IndiGo since it started operations. The two methods agree with each other till December 2008. From January 2009, when the DGCA changed its format of reporting data, the errors have been present, and have been unacceptably large and inconsistent.
The data shows that, according to computations, domestic load factors at IndiGo never crossed 90%, and that load factors crossed 80% only on 7 occasions in 9 years. Average domestic load factors at the airline, across 9 years, is recomputed as just 71.5%, with the highest at 83.3% in the month of May 2015. Of course, this arguably assumes that the number of departures and the number of passengers reported by the DGCA are correct.
Similarly, AirAsia India’s and Vistara’s load factors are not always representative of the actual load factors. In the case of these two airlines, the error is small. However, every 1% error in load factor corresponds to a monthly revenue of INR 56 lakhs for an airline the size of AirAsia India, and INR 16 crore for an airline the size of IndiGo.
Vistara’s load factors have never crossed 70%.
Below is that of Go air, for 9 months only:
Considering that the data is derived from what airlines have published, it may be that part of the onus for the error rests on airlines. It is difficult to compute the error in load factors of airlines such as SpiceJet, Jet Airways, Air India, and Air Costa.
Faith in our method of computation is based on cross checking certain computed load factors with the information revealed by a senior airline official.
On Time Performance
Airline on time performance is another parameter met with much enthusiasm. For example, for the month of April of 2015, DGCA reported that AirAsia India had an on time performance (OTP) of 100.0%. DGCA mentions the OTP as observed at only four airports: Bengaluru, Hyderabad, Mumbai and Delhi. Back then, AirAsia India was based only out of Bengaluru.
However, Bengaluru International airport, in its On Time Performance (OPT) report for April, clearly mentions AirAsia India’s arrival OTP as 89% and departure OTP as 98%. This averages to 93.5% OTP, which made headlines as 100%. (Click here for an NDTV piece on this)
Similarly, Go Air’s OTP for Bengaluru was reported by the DGCA as 88.9%, while the airport stated that the airline had an arrival OTP of 73% and a departure OTP of 86%. The DGCA’s OTP for Go Air at Bengaluru was impossibly higher than the higher of the two OTP for the airline for that month.
IndiGo’s OTP at Bengaluru was reported as 77.2%, while the airport stated that the airline had an arrival OTP of 73% and a departure OTP of 81%. In this case, the average of the departure and arrival worked out to 77%, which is acceptable.
In the case of SpiceJet, OTP at Bengaluru was reported as 68.2%, while the airport stated that the airline had an arrival OTP of 78% and a departure OTP of 78%. In this case, the reported OTP is lower than the actual OTP of 78%.
Data reported by the DGCA is very informative. The data is used by analysts and major industry bodies for studies, reports, and analysis. However, no matter how good the analysis, junk data in results in junk data out, with misleading facts and figures about the industry and the performance of airlines.
Poor data standards may give airlines a way to falsely drive up their performance figures, which may be for many reasons, such as driving up investor sentiment.
The DGCA’s capabilities (or the lack of it) have come under question both before and after the FAA downgrade. What is further disappointing is that the data published by the DGCA is not accurate enough to be used for serious academic or analytical purposes. When thumbing through the data for Jet Airways, it was brought to light that the data reported by the DGCA in its Traffic Reports and Traffic Data differ, and both differ from the data reported by the airline.
Interestingly, the errors reported in the ‘Traffic Data’ for Jet Airways as published on its site are at places huge. The ‘Traffic Reports’, released around the 15th of every month, are more accurate, but lack sufficient data for an analysis. Certain data with have an error less than 1% may be ignored on a case basis. But the question still lingers: how two publications from the DGCA can have largely differing data between them – an error that may not be attributed to rounding-off-error.
This discrepancy was brought to light only through Jet Airways’ published data. Since other airlines do not publish such data, the extent of errors and deviations are uncertain.
Further, in the month of November, two airlines, both flying with red colours, have had numerous cancellations and delays. Delays and cancellations are reported by airports. In the case of Bangalore’s Kempegowda International Airport, the airport has been using the term ‘rescheduled’ for one particular carrier (and interestingly not for any other carrier), which effectively masks both delays and cancellations. In such a case, a delayed flight, operating ‘on time’ in accordance with a ‘rescheduled’ departure timing will prevent true OTP data (though the DGCA does not yet list the OTP for the airline in question) and ‘Cancellation Rate’ from being published in Traffic Reports, making comparisons between airlines both difficult and unfair.
The DGCA has issued a public notice on the use of Unmanned Aerial Vehicles (UAV) & Unmanned Aircraft Systems (UAS) for civil applications. The public notice, which must be complied with, bans the launch of any UAS or UAV in the Indian Civil Airspace.
Such a directive has been issued in the light of potential safety issues associated with high performance UAVs interfering with flight safety. Recent sightings of ‘UFO’s by commercial airline pilots have only helped speed up such a notification.
The notice, issued on 7th October 2014, will remain in effect till the DGCA formulates regulations associated with the certification & operation of UAS in the Indian Civil Airspace, in line with what the ICAO standardizes.
Impact on Hobby Flyers
Since the DGCA’s regulations concerning UAS/UAV will be in line with those of the ICAO, ICAO definitions and policies may be adopted, in large or in entirety.
ICAO Circular 328-AN/190 concerning both UAVs and UAS, states, “In the broadest sense, the introduction of UAS does not change any existing distinctions between model aircraft and aircraft. Model aircraft, generally recognized as in tended for recreational purposes only, fall outside the provisions of the Chicago Convention, being exclusively the subject of relevant national regulations, if any”.
The communication between air traffic controllers and pilots is key to efficiency and safety in the air traffic system (ATS). Air Traffic Control Officers (ATCOs) are looked upon as managers : managing the flow of air traffic, and relaying crisp, and necessary messages to pilots.
Effective management is only possible when there is a deep understanding of the technicalities of the lower levels. A manager is always at a ‘higher level’, and decisions are based on a ‘lower levels’ of understanding. Effective management of air traffic is possible only when an ATCO understands, and not just communicates to, a pilot.
Accidents in the past have been due to gaps in understanding between ATCOs and pilots. Fuel burn and on time performance (OTP) are heavily dependent on the decisions taken by an ATCO. Once ATCOs understand aircraft, and aircraft performance, and fuel burn for every extra nautical mile and minute they make airplanes fly, things fall better in place: airline economics, better airport efficiency, and enhanced flight safety.
This piece clears the air over a possibly misleading media report in Business Today (BT), “DGCA plans to shut doors on low fuel landings”. The DGCA is right.
Delhi International Airport Limited (DIAL) is known to witness severe fog in winter, which is responsible for a significant number of flight diversions. In the winter of 2011, there were 57 diversions, which steadily grew to 89 in 2012, and 143 in 2013: a 60% yearly growth over the last three years.
To address these now unacceptable number of diversions in winter, the DGCA setup a committee in January 2014 to study the ways in which Delhi may be made a “zero diversionary airport”. The committee concluded the study with a report that included 27 recommendations, one of which was not well understood. Recommendation number 13 states, “AIP shall be amended to indicate that the term fuel emergency would not be recognised at Indian aerodromes.” That recommendation is valid, but was misunderstood by a section of the media.
Further, the BT report stated “DGCA justifies move by saying that airlines are expected to carry at least 1.5 times more fuel than what it actually requires during a flight but they generally carry less fuel.” This too shall be clarified.
An airplane is always expected to land with an amount of fuel in the tanks that is above a minimum quantity commonly referred to as “final reserve fuel”. When in flight, if the fuel quantity in the tanks dips below the reserve fuel quantity, the airplane is deemed to be in an emergency. This reserve fuel is the fuel required to fly at 1,500ft above the destination airport, for 30 minutes. For the Boeing 737-800, at typical loads, this is around 1,200kg. Larger airplanes, which consume more fuel in 30 minutes, consequently have a larger weight of fuel as reserve.
Until recently, there was no recommended standard phraseology to be used when the flight crew determined that the aircraft will infringe upon its final fuel reserves before landing. There were two widely used phrases: “Minimum Fuel”, and “Emergency Fuel”. Minimum fuel is an advisory to Air Traffic Control that should there be further delay for landing, the airplane will start eating into the reserve fuel. “Emergency Fuel” was a declaration of emergency, that the airplane has started eating into the reserve fuel. However, the interpretation of this term has been varied, with the FAA recognizing it as “The point at which, in the judgment of the pilot-in-command, it is necessary to proceed directly to the airport of intended landing due to low fuel.” Low fuel does not necessarily mean the final reserve fuel, and is a very subjective quantity.
Unfortunately, a declaration of “Emergency Fuel” would require Air Traffic Control to award the airplane priority. Priority is defined as no further delay into getting the airplane to land. This was reportedly abused by some airlines, including India’s only consistently profitable airline, to ensure that the airplane lands without burning further fuel. That is money saved.
India is a member of the United Nations (UN). The International Civil Aviation Organisation (ICAO) is a UN Agency. ICAO works with member states, and industries and aviation organizations to develop international Standards and Recommended Practices (SARPs) which are then used by states when they develop their legally-binding national civil aviation regulations (CARs). The SARPs ensure uniform best practices, and safe, efficient , and secure flights through commonly understood standards.
Effective 15th November 2012, ICAO has amended ICAO Annex 6 Part I, to include:
“The pilot-in-command shall advise ATC of a minimum fuel state by declaring MINIMUM FUEL when, having committed to land at a specific aerodrome, the pilot calculates that any change to the existing clearance to that aerodrome may result in landing with less than planned final reserve fuel.”
“The pilot-in-command shall declare a situation of fuel emergency by broadcasting MAYDAY, MAYDAY, MAYDAY,FUEL, when the calculated usable fuel predicted to be available upon landing at the nearest aerodrome where a safe landing can be made is less than the planned final reserve fuel.”
As a result, henceforth, ’Fuel Emergency’ or ‘fuel priority’ are not recognised terms. India not recognizing these two terms only aligns the country with ICAO standards, helping the country get out of safety audit downgrades.
Further, “Minimum Fuel” is only an advice to ATC, requiring no action by ATC, but “ MAYDAY, MAYDAY, MAYDAY,FUEL” is a declaration of an emergency, in which the ATC must assist the airplane in landing as soon as possible.
DGCA, in its Civil Aviation Regulation (CAR) that covers “Operation of Commercial Air Transport Aeroplanes”, states:
“A flight shall not be commenced unless, taking into account both the meteorological conditions and any delays that are expected in flight, the aeroplane carries sufficient fuel and oil to ensure that it can safely complete the flight. In addition, a reserve shall be carried to provide for contingencies.”
In accordance with the CAR, the airplane must at minimum carry the following fuel, for a flight from Bangalore to Delhi (1000NM), with 180 passengers on a Boeing 737-800W, with an assumption of no cargo. Quantities are derived from the airplane flight manuals and typical airline practices.
The fuel required to taxi from the gate to the runway.
The required fuel quantity from initiating take-off to the landing at the destination airport.
Typically 5% of the Trip fuel, but can be as high as 10%. caters to unforeseen circumstances or prediction errors.
The fuel required to execute a missed approach at Delhi and fly to an alternate airport (Jaipur in this case), in case landing at Delhi is not possible, due to issues like visibility.
Final Reserve Fuel
The final reserve fuel is the minimum fuel required to fly for 30 minutes at 1,500 feet above the alternate airport.
Based on statistically derived data at the airline, and also at the discretion of the Captain (based on his judgement and reports of a congested airport, or bad weather, or the like.) Assumed Zero for this example.
The sum of the fuels 1 – 6, which must be uplifted at the departure airport.
If the flight goes as planned, the aircraft should consume only the trip fuel, which amounts to 6,000kg. But the aircraft is filled with 9,000 kg of fuel, which is 1.5 times that of the trip fuel.
One of longest domestic flights into Delhi is from Bangalore, the others being from Chennai and Cochin. As flights get longer, the total fuel will fall below 1.5 times the trip fuel. As flights get shorter, the total fuel will amount to greater than 1.5 times the trip fuel. Since the Bangalore – Delhi flight is one of the longest domestic flights into Delhi, BT’s “DGCA officials” were not off the mark with a ballpark 1.5 figure, but that is a number that is written nowhere, must never be used for planning, and should not have been quoted in the first place. The Mumbai-Delhi sector (which is shorter) will consume only 4,000kg of fuel, but will need to legally carry a minimum of 6,900kg of fuel, which is 1.7 times the trip fuel.
1. The DGCA’s recommendation is not “highly controversial”, as reported by BT. The ambiguous term “fuel emergency” is not recognized and is replaced by standard phraseologies as described above. Flight safety is not compromised but rather improved.
2. DGCA cannot “shut doors” on low fuel landings, as reported. That means you can’t land if you’re low on fuel. What DGCA is doing is to ensure certain standard terminologies are used, doing away with old ones.
2. The laws are not ” draconian”, but progressive to keep up with ICAO standards.
3. A “1.5” figure is not justified, as it depends on many factors. However, if the DGCA official used it to throw a ball park ratio, he’s not off the mark. But later in the BT article is probably a typo which is misleading, “expected to carry at least 1.5 times more fuel“. It must read 1.5 times the trip fuel.
Edit: Added Cochin & Chennai to Delhi as other long flights into Delhi. Thanks to Cyril.
The U.S. Department of Transportation’s Federal Aviation Administration (FAA) today announced that India has been assigned a Category 2 rating under its International Aviation Safety Assessment (IASA) program, based on a recent reassessment of the country’s civil aviation authority. This signifies that India’s civil aviation safety oversight regime does not currently comply with the international safety standards set by the International Civil Aviation Organization (ICAO); however, the United States will continue to work with India’s Directorate General for Civil Aviation (DGCA) to identify the remaining steps necessary to regain Category 1 status for India. With a Category 2 rating, India’s carriers can continue existing service to the United States, but will not be allowed to establish new service to the United States.
India achieved a Category 1 rating, signifying compliance with ICAO standards, in August 1997. A December 2012 ICAO audit identified deficiencies in the ICAO-set global standards for oversight of aviation safety by India’s Directorate General of Civil Aviation (DGCA). Subsequently, the FAA began a reassessment of India’s compliance with ICAO standards under the FAA’s IASA program, which monitors adherence to international safety standards and practices. The FAA has consulted extensively with the DCGA and other relevant Indian government ministries during its evaluation, including consultations in India in September and early December, and meetings this week in Delhi.
“U.S. and Indian aviation officials have developed an important working relationship as our countries work to meet the challenges of ensuring international aviation safety. The FAA is available to work with the Directorate General of Civil Aviation to help India regain its Category 1 rating,” said FAA Administrator Michael Huerta.
The Government of India has made significant progress towards addressing issues identified during the September 2013 IASA assessment. On January 20, the Government of India took further steps to resolve outstanding issues when the Indian Cabinet approved the hiring of 75 additional full-time inspectors. The United States Government commends the Indian government for taking these important actions, and looks forward to continued progress by Indian authorities to comply with internationally mandated aviation safety oversight standards.
Additional Background on the FAA’s IASA Program:
As part of the FAA’s IASA program, the agency assesses on a uniform basis the civil aviation authorities of all countries with air carriers that operate or have applied to operate to the United States and makes that information available to the public. The assessments determine whether or not foreign civil aviation authorities are meeting ICAO safety standards, not FAA regulations.
A Category 2 rating means a country either lacks laws or regulations necessary to oversee air carriers in accordance with minimum international standards, or that its civil aviation authority – equivalent to the FAA for aviation safety matters – is deficient in one or more areas, such as technical expertise, trained personnel, record-keeping or inspection procedures.
Countries with air carriers that fly to the United States must adhere to the safety standards of ICAO, the United Nations’ technical agency for aviation that establishes international standards and recommended practices for aircraft operations and maintenance.
Deccan Charters’ VT-DCE, which has a G1000 flight deck. The G1000 supports data logging, sufficient for FDM and FOQA needs.
The Flying Engineer explores regulations covering flight recorders, and how even in the absence of the mandate for such devices in single engine and piston aircraft, a commonly found avionics suite allows the operator to tackle flight safety: proactively.
The Indian Director General of Civil Aviation (DGCA), in its civil aviation regulations (CAR) Section 2 Series “I” Part V Issue II, dated 23rd January 2013, covers flight data recorders (FDR), and describes a FDR as “Any type of recorder installed in the aircraft for the purpose of complementing accident/incident investigation.”
The same regulation does not talk about FDR for single engine airplanes. The closest it comes to is a recommendation, for commercial transport, and general aviation, “that all turbine-engined aeroplanes of a maximum certificated take-off mass of 5700kg or less for which the individual certificate of airworthiness is first issued on or after 1 January 2016 should be equipped with: a) a Type II FDR; or b) a class C AIR capable of recording flight path and speed parameters displayed to the pilot(s);or c) an ADRS capable of recording the essential parameters”
A recommendation is not enforceable, and single engine pistons are not covered.
Interestingly, CAR Section 3 (Air Transport) Series C Part III Issue II, dated 1st June 2010, talks of the minimum requirement for the grant of a Non-Scheduled Operator Permit (NSOP). The CAR covers single engine turbine, and single engine piston aircraft as well. The regulation also describes the need to demonstrate a “Flight Operations Quality Assurance (FOQA) and CVR/FDR monitoring system.”
Flight Data Monitoring (FDM) is defined as “the pro-active use of recorded flight data from routine operations to improve aviation safety.” FDM is important, as a review of recorded flight can identify deviations and exceedances, which can be used for corrective training. It is an effective method where an incident is analyzed, and brought to the notice of flight & maintenance crew before it amplifies to an accident.
The surprise here is the DGCA’s realization of the importance of FDM & FOQA in aviation, irrespective of the airplane type, but it’s very regulations do not cover FDRs in single engine airplanes.
Infact, piston engine, whether multi or single engine, are not covered: “All multi-engined turbine powered aeroplanes of a maximum certificated takeoff mass of 5700kg or less for which the individual certificate of airworthiness is first issued on or after 1 January 1989, shall be equipped with a Type II FDR by 31.12.2013.”
Either DGCA assumes that pistons have no future, or that operators, both commercial and general aviation, fly only turbines.
The benefits of FDM
FDM is beneficial for everybody, right from the student pilot to the airline pilot. In training, FDM is necessary to immediately identify exceedances and deviations, bringing it to the notice of the concerned. For example, a student pilot who pulled a high G maneuver may have stressed an airframe, and if before scheduled inspections, the airframe is stressed multiple times, a failure could result. Similarly, a private pilot with 50-60 hrs may make mistakes, which may go unnoticed unless an expert, or a sufficiently experienced person goes through the flight data recordings to understand and point out what went wrong, and how it may be avoided. These are small steps toward enhanced safety for all.
Flight Data Recording without a FDR
G1000 for a Cessna 172
Garmin’s G1000 has been adopted by many airframe manufacturers, making it a standard fit on their aircraft. Cessna for one, offers the G1000 from the 172R to its turbine single engines, including the Grand Caravan.
The Garmin G1000 features flight data logging (FDL), which is not a FDR, but may be used for the same purpose: FDM & FOQA.
On the 172, the G1000 for Cessna: NAV III, logs 64 parameters, at a 1 second interval. These parameters cover (and exceed) the requirements laid down in the regulations for an Aircraft Data Recording System (ADRS), but fall short on only 2 aspects: the recording interval (some data needs to be recorded at 250ms intervals, but is logged in the G1000 in 1 second intervals), and the control surface position (primary and secondary flight control positions are not recorded).
States the Garmin Manual, “The Flight Data Logging feature will automatically store critical flight and engine data on an SD data card inserted into the top card slot of the MFD. Approximately 4,000 flight hours can be recorded on the card.”
In addition, Garmin provides a free, simple to use software that in a few clicks converts the recorded flle to a Google Earth path, which can be viewed in 3D to visually analyze the flight path.
A side-by-side shot of the regions of the MFD where the SD card for flight logging is inserted. One aircraft has it inserted, while the other has it missing, losing the benefits of FDM.
The Flying Engineer has flight data logs from a Cessna 172R for two flights spanning over 2 hours, and the parameters have been so exhaustive that it has supported academic use of the data.
VT-FGE, the ill-fated Diamond DA40CS that crashed in the December of 2013 when on a training flight, has the logging functionality. With the log, it will be immediately clear as to what went wrong, playback of which will prevent other students from repeating the same mistakes.
Unfortunately, schools and some private operators record the data, but do not have a program to pro-actively monitor and analyze every flight, every day, missing an opportunity to self learn and proactively enhance flight safety.
The DGCA, India, issued a new Civil Aviation Requirement, SECTION 8 – AIRCRAFT OPERATIONS SERIES ‘C’ PART I(click for PDF) on the 13th of June, 2011, on All Weather Operations (AWO). Due to the extended operational impact of this CAR, a great amount of Jeppesen charts were affected. (See Chart Alert), the most noticable of which is a grey shaded box in the profile.
Note the "Grey Area" in the approach profile.
The CAR lays out that all non-precision approaches (NPA) shall be flown using the Continuous Descent Final Approaches (CDFA) technique unless otherwise approved by the DGCA for a particular approach to a particular runway.
Compared to the traditional descent approach technique, where the aircraft descends step-by-step prior to the next minimum altitude, the CDFA technique has safety and operational advantages, such as standardization of procedures, simplification of the decision process (one technique, one decision at one point), increased height above obstacles, use of a stable flight path, reduced noise and reduced fuel burn. The CDFA technique can be flown on most published approach when VNAV or ILS is not available. When electronic or a pre-stored computed vertical guidance is not used, vertical speed or flight path angle may be used to achieve a CDFA profile.
This has few implications. Air crews can no longer level out at the MDA and fly to the MAP to execute a go around. Instead, the go-around must be executed at the MDA, or the MAP, whichever occurs first. Also, the go around must be flown through the MAP, unless otherwise specified. Hence, the pull up arrow is at the point where the CDFA and the MDA intersect.
In case of ILS approaches, the CDFA and the Glide path are identical. The CDFA is enforced when the Glide Slope is out of service, in which case, go-around must be initiated at the point where the glide path and the MDA intersect.
Because the concept of levelling off at MDA no longer exists, there are chances of flying below the MDA, in case of executing a missed approach at MDA when flying a CDFA. Further, the MDA may be reached either before or after the intended vertical path, due to vertical path errors involved with a non-precision approach. For this reason, the MDA is emphasised in the segment between the MAP and the ALTITUDE-DME check preceding the MAP.
The Jeppesen chart profile depiction will be modified to show the continuous descent on final approach. DGCA published minimum altitudes will be shown as segment minimum altitudes in the profile (grey shaded box). These minimum altitudes are typically provided for obstacle clearance and must not be violated to remain clear of obstacles or terrain.